Vaso-occlusive Crisis Research Articles

Impact of Srs-CoV2 Infection on Pain Crises and Acute Chest Syndome in Patients with Sickle Cell Anemia: A Retrospective Multi-Cohort Study Based on USA Data from 2020-2022

Objective: To determine the impact of SARS-CoV-2 infection on vaso-occlusive pain crisis (VOC) and acute chest syndrome (ACS), incidence, and outcomes in sickle cell anemia (SCA) patients. Method: This retrospective study used the TriNetX USA health research network database to identify SCA patients (Hb-SS, Sβ0-thal) ages 1-50 with and without concomitant SARS-CoV-2 infection from May 2020 to May 2022. A total of 6 cohorts were created: pain crisis with/without SARS-CoV-2, ACS with/without SARS-CoV-2, and SARS-CoV-2 without pain crisis/ACS. Patients with SARS-CoV-2 and pain crisis/ACS were compared to 2 cohorts (SARS-CoV-2 without pain crisis/ACS) for demographic characteristics, baseline laboratory parameters, disease-modifying drug use, and influenza/COVID-19 vaccination status by t-tests. Pain crisis/ACS patients with SARS-CoV-2 were then compared to 2 cohorts (pain crisis/ACS without concomitant infection) for demographic characteristics, and relative risk for acute settings of care, pain control, laboratory parameters/outcomes (including hemolytic and inflammatory markers), procedures (blood transfusion) and mortality. Results : The incidence of pain crises and ACS in SCA patients following SARS-CoV-2 infection was 34 and 27 per 100 patients, respectively. The risk of developing ACS was significantly increased by SARS-CoV-2 infection (2.57% vs. 1.17%, RR 2.2), but not the risk of developing a pain crisis (RR 1.04). Pain crisis and ACS patients with concomitant SARS-CoV-2 infection had a greater risk for inpatient services, subsequent hospital visits, opioid and non-opioid analgesia, blood transfusions, and concerning hemolytic and inflammatory markers compared to those without the infection. Patients with SARS-CoV-2 who did not develop pain crises/ACS had higher baseline hemoglobin levels prior to infection compared to patients who developed pain crisis/ACS. There was a higher rate of COVID-19 and influenza vaccination in the cohorts who did not develop pain crisis/ACS and might have improved pain crisis rates (but not ACS) following SARS-CoV-2 infection. Conclusions: COVID-19 illness had an impact on the incidence of both pain crises and ACS, significantly increased the risk of developing ACS, and influenced morbidity outcomes for both pain crises and ACS. Prior vaccination against influenza and COVID-19 may represent a protective factor for developing pain crises.

Steady-State Von Willebrand Factor Antigen Levels Predict Low Platelet Counts and Risk for Complications in Hospitalizations for Painful Sickle Cell Vaso-Occlusive Episodes

We previously reported that a >20% decline in platelet counts from steady state to presentation predicted severe complications during hospitalization for vaso-occlusive pain crisis (VOC) in 130 adult sickle cell disease (SCD) patients. 1 Sharp platelet decline in acute chest syndrome was reported to be accompanied by large von Willebrand Factor (VWF) aggregates adherent to pulmonary vascular endothelium in SCD. 2 A prospective study of 24 SCD patients found a significant increase of VWF reactivity in VOC admissions relative to steady state, which correlated with low platelet counts and the development of acute chest syndrome. 3 We aimed to investigate the role of steady-state VWF antigen level and ADAMTS13 activity as predictors of platelet count decline and severe complications in VOC admissions. Plasma levels of VWF antigen and ADAMTS13 activity were measured 4 for 56 patients at steady-state outpatient visits (Baseline). VWF antigen was expressed as fold increase or decrease from the concentration in normal pooled plasma of 12.2 ug/ml; ADAMTS13 activity was expressed as fold of the value from normal pooled plasma which was considered 100% activity. Electronic records of VOC admission that occurred >21 days after Baseline were reviewed. Exclusion criteria included non-VOC admissions defined as elective admission for surgery, admission for accident or injury, admission for delivery of an infant, or admission with a pain score <8/10 at presentation. 5 A total of 98 qualifying admissions were identified. Severe complication during the admission was defined as having any of the following: 1) acute chest syndrome, new infiltrate on chest X-ray, or use of ventilator; 2) acute kidney injury; 6 3) acute liver injury; 7 4) thrombotic or hemorrhagic stroke; 5) venous thromboembolism including deep vein thrombosis, atrial thrombosis, and pulmonary embolism; 6) need for transfer to the intensive care unit; 7) need for exchange blood transfusion; 8) death during hospitalization. Platelet counts at presentation to the emergency room (ER) leading to the admissions under study were recorded, as well platelet counts at Baseline. The 56 patients had a median (range) age of 37 (21-66) years; 52% are female, 89% with hemoglobin SS or Sβ 0-thalassemia, and 57% on hydroxyrea (HU). Severe complication occurred in 35 (36%) of the 98 admissions involving 27 (48%) of the patients. Focusing on the first admissions, higher steady-state VWF antigen levels correlated strongly with lower ER platelet counts (ρ= -0.50, P=0.00011, Figure 1A) and higher steady-state ADAMTS13 activity correlated weakly with ER platelet counts (Spearman's ρ= 0.30, P=0.025). The ratio of VWF antigen to ADAMTS13 activity ratio also correlated strongly with lower ER platelet counts (ρ= -0.52, P=0.000052, Figure 1B). In contrast, steady-state VWF antigen level (ρ= -0.17, P=0.23), ADAMTS13 activity (ρ= 0.19, P=0.17), and VWF antigen to ADAMTS13 activity ratio (ρ= -0.23, P=0.098) showed no significant correlation with steady-state platelet counts. The correlations remained by adjusting for age, gender, Hb genotype severity, HU, and treatment of anticoagulant, aspirin, or non-steroidal anti-inflammatory drugs at VOC visits. In analyses restricted to admissions >1 year after Baseline, the correlation between steady-state VWF antigen level and ER platelet counts appeared to persist. Focusing on the 28 first admissions, steady-state VWF antigen level (ρ= -0.50, P=0.0071) and VWF antigen to ADAMTS13 activity ratio (ρ= -0.44, P=0.018) correlated negatively with ER platelet counts. Steady-state ADAMTS13 activity did not correlate with ER platelet counts in admissions that occurred >1 year after Baseline (ρ= 0.16, P=0.43). We further examined the association of steady-state VWF antigen level, ADAMTS13 activity, and their ratio with risk for severe complication in admission. Focusing on the first 56 admissions, which involved 23 complications, steady-state VWF antigen level in the top quartile (1.63) associated with risk for severe complications (OR=6.5, 95% CI 1.4-31, P=0.018, n=56), adjusting for age, gender, Hb genotype severity, and HU. Our observations suggest that steady-state VWF antigen level and the ratio of VWF antigen level to ADAMTS13 activity predict low platelet counts at presentation to VOC admissions, and that steady-state VWF antigen level in SCD patients may be a relatively stable marker for risk of severe VOC complications.

17R-Resolvin D1 Improves Inflammatory Cardiomyopathy in a Mouse Model of Sickle Cell Disease

Sickle cell disease (SCD) is a severely invalidating genetic red cell disorder. Inflammatory vasculopathy and cardiopulmonary complications markedly impact quality of life and survival. Limited studies are available on the pathogenesis of sickle cell related cardiomyopathy. However, the combination of inflammatory vasculopathy, heart ischemia, and myocardial fibrosis have been suggested to play a role in sickle cell related cardiomyopathy. This is supported by the amelioration of cardiomyopathy in SCD patients, early and intensively treated with either hydroxyurea or chronic transfusion regimen (Niss O et al. Blood 140: 1322, 2022). Recently, we have highlighted an impairment of pro-resolving events in SCD with a deleterious effect on acute sickle cell related organ damage (Matte A et al. Blood 133: 252, 2019). Growing evidence links impairment of pro-resolving mechanisms with atherosclerosis and ischemic cardiomyopathy (Kain V et al. J Mol Cell Cardiol 84: 24, 2015; Conte MS et al. JCI 128: 3727, 2018). Among specialized pro-resolving mediators, 17R-resolvin D1 (17R-RvD1) has been shown to play important protective actions in cardiovascular diseases (Kain V et al. J Mol Cell Cardiol 84: 24, 2015). Here, we first determined the appropriate window of time to study cardiac response to hypoxia/reoxygenation (H/R) stress, mimicking sickle cell related acute vaso-occlusive crisis. We show that humanized SCD mice (TT model) exposed to H/R (10 hours hypoxia 8% oxygen, followed by 3 hours reoxygenation) display increased markers of myocardial dysfunction with neutrophil heart infiltration compared to either SCD mice under normoxia or to healthy (AA) animals exposed to H/R stress. With integrated proteomic and miRNA analyses we have identified upregulation of proteins and miRNAs involved in fibrosis, hypertrophy of the heart, and cardiomyocyte apoptosis. Differentially expressed miRNAs in SCD-hearts compared to AA included miR-16-5p, miR-122-5p, and miR-206-3p, which are involved in angiogenesis and heart fibrosis and hypertrophy. Upregulated proteins in SCD hearts in response to H/R encompassed: NF-kB, Nrf2, hemeoxygenase-1, glutathione peroxidase, and peroxiredoxins (associated to response to oxidative stress), the profibrotic factors FGF and PDGF as well as the TGF-ß1 receptor, and the pro-angiogenic VEGF pathway. Treatment with 17R-RvD1 (100 ng administrated by gavage 1 hour before H/R, see also Matte A et al. Blood 133: 252, 2019) protected heart of SCD mice from H/R-induced stress as supported by significant reduction of ANP, a marker of cardiovascular dysfunction, decrease in neutrophil infiltration, and NF-kB activation (Figure 1). 17R-RvD1 also diminished the H/R-driven upregulation of miR-16-5p, while it enhanced miR-206-3p that was downregulated by H/R, suggesting that 17R-RvD1 can reduce cardiac fibrosis and other pathological processes associated with these miRNAs in SCD. We also found that 17R-RvD1 administration to SCD mice blunted the activation of TGF-ß1 pathway and of markers of extracellular remodeling, supporting the beneficial effect of 17R-RvD1 against H/R stress. Taken together, our data show that 17R-RvD1 reduced heart remodeling and fibrosis in SCD mice undergoing H/R, a model of acute VOCs. This improved understanding in basic pathophysiology of SCD-related inflammatory cardiomyopathy, providing new evidence for protective therapeutic effects of 17R-RvD1 on SCD cardiovascular diseases.

Ineffective Erythropoiesis with Aging in Adults with Sickle Cell Disease

INTRODUCTION In the United States, life expectancy for adults with sickle cell disease (SCD) has improved over the last several decades and providers are now encountering increasing numbers of patients in the fourth, fifth and sixth decades. One notable feature of older SCD patients is lower ‘steady state’ hemoglobin (Hb) levels. Although it is well established that lower Hb levels are associated with increased adverse outcomes including pulmonary hypertension, stroke, cognitive decline, acute chest syndrome, frequency of vaso-occlusive crisis and shortened survival, a full understanding of the mechanisms accounting for the more prevalent and severe anemia in older SCD patients remains to be elucidated. Involved factors may include the long-term effect of chronic hemolysis, age-associated increased inflammation, progressive renal insufficiency and an age-related decline in nutritional adequacy. Despite lacking a uniform explanation for anemia applicable to individual SCD patients, it remains a management goal to optimize Hb level as possible within constraints associated with the development of secondary hemochromatosis. We postulate that the pathways to anemia in SCD patients may change with advancing age and that a better understanding of these pathways may result in a more directed intervention for the older sickle cell patient. METHODS Adult patients visiting Inova Adult Sickle Cell Center over a 6-month period (January through June 2023) with Hb levels below 9 g/dL were evaluated by a contemporary hematologic panel that included complete blood count with differential, reticulocyte count, comprehensive metabolic panel (included total bilirubin and creatinine), and lactate dehydrogenase (LDH). The reticulocyte proliferation index (RPI) was determined utilizing a readily accessible calculator (MedCalc) and a univariate regression analysis was performed for RPI against age. An RPI of < 2 was considered evidence for hypoproliferative anemia. RESULTS Of the 139 unique adult SCD patients visiting our clinic in this 6-month period, 60 had Hb levels equal to or below 9 g/dL. Of these, 8 patients had serum creatinine levels ≥ 1.5 mg/dL and were considered to have hypoproliferative anemia based on renal insufficiency. Among the remaining 52 patients, the mean age was 34.9 years, mean Hb was 7.49 g/dL and the mean RPI was 2.52. In patients with age ≤ 40 years, mean RPI was 2.74, compared to mean RPI of 1.61 in patients with age > 40 years. The mean Hb was 7.55 g/dL vs 7.21 g/dL mean total bilirubin was 3.08 mg/dL vs 2.15 mg/dL and mean LDH was 509 U/L vs 434 U/L in these two age groups (Fig 1). Regression analysis indicated that an increase in age corresponded to a reduction in RPI at 95% confidence level (Fig 2; regression coefficient: -0.04; 95% CI: -0.08 - -0.003; p-value: 0.03). CONCLUSION From the data we gathered, we conclude that despite chronic hemolysis in sickle cell disease, low RPI and ineffective erythropoiesis are evident to some extent in the majority of adult SCD patients even in the absence of renal failure and this significantly increases with age. Older patients with SCD are more likely to have ineffective erythropoiesis. We speculate that this may be evidence for age-associated bone marrow failure not unlike myelodysplasia (MDS) which occurs with increased frequency in the general population with advancing age. If future studies confirm disordered erythropoiesis, clonal hematopoiesis, or other markers of MDS, novel treatments known to be effective in patients with MDS may be examined in selected anemic SCD patients.

Partial Red Cell Exchange Is an Effective Tool for Adequately Reducing Hemoglobin S Levels in Patients with Sickle Cell Disease and Improving Patient Outcomes Including Reduction in Acute Care Utilization

Introduction: Red cell exchange (RCE) is a therapeutic procedure that aims to reduce the number of sickle-shaped red blood cells in circulation and replace them with healthy donor cells. The use of red cell exchange in sickle cell disease (SCD) is primarily aimed at preventing or treating acute complications such as acute chest syndrome, stroke or priapism. However, in patients with inadequate disease control and associated frequent hospitalizations requiring parenteral opioids, we have proposed that prophylactic partial RCE (pRCE) be incorporated into the treatment plan. Implementation of pRCE with resulting limitation of parenteral opioid use may potentially reduce hospitalizations and achieve overall better disease control. Use of pRCE for disease control remains limited as it is labor intensive and requires copious amounts of blood which can be challenging especially in this era of COVID19 pandemic blood shortage. For this reason, we have utilized pRCE at our institution. Here we demonstrate that pRCE with four to five units of packed red blood cells (pRBCs) is equally effective in reducing hemoglobin S to levels below 40% and SCD related complications including VOCs and hospitalizations. Methods and Results: In our center, we identified six individuals with frequent hospitalizations and significant daily oral morphine equivalent requirements. These patients were then placed on a monthly pRCE protocol. Patients with variable genotypes were enrolled including HbSS, HbSC and HbSβthal +. Each patient underwent pRCE initially utilizing four units. Hemoglobin S level was closely monitored and if the target level of <40% was not reached with four units, the number was increased to five units. It is important to note that partial exchange was utilized only in patients whose indication for RCE was pain and frequent hospitalizations rather than history of CVA. In addition to pRCE, each patient was placed on a restricted care protocol that comprised of the administration of only home oral opioids during acute care visits. Prior to initiation of both pRCE and restricted care plan, patients were educated at length and during frequent clinic visits regarding the difference between chronic pain management and acute vaso-occlusive crisis. As shown in Figure 1, partial exchange leads to adequate reduction of hemoglobin S levels immediately post exchange that remains suppressed over the four-week period to predominately below 40 percent. This reduction in hemoglobin S levels results in patient-reported improved sense of well-being and compliance with restricted care plans to limit acute care utilization and move SCD care to the outpatient setting. In fact, we saw a dramatic reduction in hospitalization among patients with sickle cell disease regardless of genotype, age and gender. As shown in Figure 2, for each patient placed on restricted care plan, acute care utilization was reduced compared to each patient's previous year's monthly admission rates. Conclusion: Prolonged uncontrolled SCD with frequent VOCs will undoubtedly result in high acute care utilization, high opioid requirements and risk of development of chronic pain with subsequent opioid induced hyperalgesia and opioid failure. Partial red cell exchange is an effective tool for addressing sickle cell disease complications and improving patient outcomes, particularly in patients with least disease control and highest acute care utilization.

Differing Definitions of Vaso-Occlusion in Clinical Studies of Sickle Cell Disease Can Result in Differing Outcomes

Background: Frequent episodes of vaso-occlusion are the hallmark of sickle cell disease (SCD), but the definition of what constitutes a vaso-occlusive episode is not consistently applied across clinical trials, creating challenges in evaluating and comparing efficacy results among different therapies. Here, we compare vaso-occlusion endpoint definitions from clinical trials for various therapies, including genetic therapies, and use clinical trial data to demonstrate the potential for outcomes differences based on differing definitions of vaso-occlusive episodes. Methods: We reviewed completed and ongoing clinical trials and published articles using endpoints assessing the reduction or elimination of vaso-occlusive crisis/events, including trials of (i) exagamglogene autotemcel (exa-cel, CRISPR/Cas-9 based genome editing treatment), (ii) lovotibeglogene autotemcel (lovo-cel, gene addition therapy), (iii) L-glutamine, (iv) voxelotor, (v) hydroxyurea (HU) and (vi) crizanlizumab. Outcomes related to vaso-occlusion were compared across variables including care setting, care duration, treatments, and complications. Data from the CLIMB SCD-121 trial of exa-cel in patients aged 12 to 35 years with severe SCD (data cut as of 10 Feb 2023) were evaluated using different published definitions of vaso-occlusion. Results: The most substantial differences in vaso-occlusion endpoint definitions were associated with frequency and duration of visits to medical facilities for acute pain and inclusion of specific SCD specific complications. Definitions of vaso-occlusions for acute pain related events differed across studies. The definitions of severe vaso-occlusive crises for exa-cel (severe VOC; exa-cel), sickle cell pain-related crises (SCPC; crizanlizumab and L-glutamine), and VOC (VOC; voxelotor) include events with medical facility visits of any duration (severe VOC and SCPC) or medical records of a patient being seen or contacting a physician within 1 business day of an event (VOC), whereas the definition of severe vaso-occlusive events (severe VOE; lovo-cel) requires a ≥ 24-hour hospital or emergency room (ER) observation unit visit or ≥2 visits to a day unit or ER over 72 hours. Vaso-occlusion definition for HU (painful crisis) required a facility visit of ≥4 hours duration. All endpoints include acute chest syndrome and priapism; however, the definition of severe VOE requires ≥4 visits to a medical facility for priapism to meet criterion, while others require only a single visit. The exa-cel phase 3 trial in SCD employs a broad and inclusive definition for severe VOC which counts each individual medical facility visit, regardless of frequency or duration of hospitalization. Based on this, 19 out of 20 patients (95%) met the primary endpoint of freedom from severe VOCs for at least 12 consecutive months (95% CI, 75.1%, 99.9%; P<0.0001). However, when the primary endpoint was analyzed using the severe VOE definition, all patients (20/20; 100.0%) were free from severe VOEs for at least 12 consecutive months (95% CI: 83.2%, 100.0%; P<0.0001). Conclusions: Requirements for health care facility visits in the definitions of severe VOC (exa-cel), VOC, and SCPC were more broadly inclusive and include events that would not be counted in the definitions of severe VOE (lovo-cel) or painful crisis. Clinically, support for this observation comes from our analysis of exa-cel SCD pivotal clinical trial data using these different definitions, which showed the number of patients free from vaso-occlusive episodes changed depending on the definition of vaso-occlusion employed. These results show differences in vaso-occlusion definitions have the potential to impact assessments of treatment efficacy across different SCD therapies.

Duffy-Null Patients with Sickle Cell Disease Are at Risk for Low Neutrophil Counts with HU Treatment

Introduction The Duffy blood group consists of two main antigens, Fya and Fyb, and is encoded by the atypical chemokine receptor 1 ( ACKR1) gene. About 60% of Black individuals have the Duffy null phenotype, Fy(a-b-) characterized by absence of expression of the Fya and Fyb antigens on red cells. The Duffy null phenotype in Black individuals is caused by homozygosity for a SNP (rs2814778; T>C; CC) in the ACKR1 gene promoter. This polymorphism results in the disruption of a binding site for the GATA1 erythroid transcription factor and silences expression of the Duffy antigens. There is a strong correlation between the Duffy null phenotype and the lower range of absolute neutrophil counts (ANC) observed in some Black individuals. The impact of Fy(a-b-) status on clinical outcomes in individuals with sickle cell disease (SCD) is not well studied. Neutropenia is a common toxicity with hydroxyurea (HU) in the treatment for SCD. We hypothesized that SCD patients with the Duffy null phenotype are at risk for lower ANCs with HU treatment, and potentially have different clinical outcomes compared to Duffy-positive patients. Methods Pediatric patients with SCD (HbSS and HbSB 0-thalassemia) treated with HU and enrolled in the St. Jude Children's Research Hospital observational cohort study, the Sickle Cell Clinical Research and Intervention Program (SCCRIP) were eligible. Patients who had available Duffy genotype and reached a maximal tolerated dose (MTD) of HU before 12/31/2021 were included. The MTD based on neutrophil counts was considered to be achieved at a dose when the ANC was between 1000 and 3000 /mm 3. Multivariate generalized linear regression model was used for association analysis after adjusting for age at HU initiation, sex, and 5 principal components. Mediation analysis was conducted to evaluate indirect effect of the Duffy null phenotype on time to MTD via baseline ANCs. Results A total of 250 patients met the inclusion criteria. One hundred eighty (72%) patients were Duffy null, and 70 (28%) patients were positive for at least one of Duffy antigen. The average patient age at starting HU was 5.9 ± 4 years old. Female patients accounted for 44.8% (n= 112) of the study population. The mean MTD of HU was 28.0 ± 5.5 mg/kg/day, the time to MTD was 2.3 ± 2.7 years, and there was no significant difference between Duffy-null and Duffy-positive patients. The Duffy null phenotype was associated with a significantly lower baseline ANCs (Duffy-null: 3800 ± 2684 /mm 3 vs. Duffy-positive: 4702 ± 3015 /mm 3; p = 0.005; Figure A), and more frequent episodes of ANC <1500 /mm 3 in the first two years after starting HU (Duffy-null: 1.2 ± 2.3 times/patent vs. Duffy-positive: 0.5 ± 1.2 times/patient; p = 0.006; Figure B). Although the Duffy null phenotype did not have a direct effect on the time to MTD, it affected the time to MTD indirectly via baseline ANC (mediation indirect effect test p = 0.01) since the higher the baseline ANCs were, the longer it took to reach MTD (p = 0.0002). We did not find the Duffy null phenotype associated with Hgb, MCV and HbF at base line, one or two years after starting HU. In addition, there was no association of Duffy status on frequencies of vaso-occlusive crisis and acute chest syndrome within 2 years after HU initiation. Notably, MCV increased significantly after HU initiation (Baseline: 83.5 ± 7.6 fl; two-year post HU: 99.0 ± 12.0 fl; p <0.00001), the increases were similar between Duffy-null and Duffy-positive patients (p = 0.36), suggesting similar HU adherence. Conclusion Patients with SCD and the Duffy null phenotype have more frequent episodes of lower ANC with HU treatment. However, Duffy status was not associated with risks for other adverse clinical outcomes.

How Sensitive Is the Sickle Prep? Clinical Implications

Introduction The sickle cell solubility test, commonly known as “sickle prep” is a qualitative measure that relies on the property that deoxygenated hemoglobin S (HbS) is insoluble. Accordingly, blood samples drawn from individuals with circulating HbS appear cloudy when mixed with sodium hydrosulfite. 1 The sickle cell solubility test has been reported to be very sensitive (99%) and specific (99.9%) for detection of HbS. However, false negatives have been reported to occur in sickle cell disease (SCD) patients with severe anemia or high levels of hemoglobin F. 2,3 In those situations HbS levels may be very low and it remains unclear what level of HbS is required for the solubility test to be positive. To address this issue, we have examined the sickle cell solubility test in a cohort of SCD patients undergoing red cell exchange, acknowledging that in many of these patients, HbS levels fall below 15% when tested immediately after completing the exchange procedure. Methods 118 patients with sickle cell anemia were screened based on outpatient visits to the Inova Adult Sickle Center from January 1, 2023 - March 31 st, 2023. Of these, 6 patients were excluded from analysis due to lack of recent sickle cell solubility test during this period. Of the total number of patients included in the analysis (n=112), 25 (22%) underwent red cell exchange during this period. For each individual, the two most recent HbS percentages with the concurrently-determined sickle cell solubility result (positive or negative) were analyzed. We examined the data in the context of known genotype (HbSS, HbSC, HbSβ 0, HbSβ +positive). In patients undergoing red cell exchange, the most recent pre and post transfusion hemoglobin S percentage were collected. Results: 200 distinct HbS levels were collected and analyzed. Of those, 5/200 tested negative for the sickle cell solubility test, yielding an overall sensitivity rate of 98%. Of those 5 patients, 4/5 had received a red cell exchange during this period, and (1/5) had severe transfusion dependent anemia. Of those with a negative sickle cell solubility test, 4/5 patients had an SS genotype, and 1/5 had SC genotype. In patients who received red cell exchange, the sensitivity rate for the sickle cell solubility test is 84%. For all patient samples with HbS >15%, the sickle solubility test was 100% sensitive. However, among the 11 samples with HbS levels below 15%, 5 were sickle prep negative thereby indicating a reduced sensitivity (55%) below that threshold. Nine (9) out of the 11 samples were of patients who had undergone red cell exchange. Conclusion: The sickle cell solubility is a very sensitive measure to establish the presence of HbS, but must be interpreted with caution in those with HbS concentrations of <15%. Because it is readily available (typically resulted within an hour) it may be of benefit in emergency departments for patients for whom there is question about the validity of the sickle cell diagnosis. At our institution, this has been a valuable addition to the initial management of patients for whom medical records are not available and who present with apparent acute vaso-occlusive crisis. We do not propose withholding analgesia for patients with a reported history of sickle cell disease pending this test, but rather recommend its use as a confirmatory test for patients presenting with a reported history of this disease.

Comorbidities of Sickle Cell Disease with Obstructive Sleep Apnea

BACKGROUND Sickle cell disease (SCD) is a devastating inherited disease process that greatly impairs quality of life and lifespan. It is a common genetic hemoglobinopathy that is vulnerable to hypoxemia due to the sickling property of red blood cells. Desaturation of the hemoglobin S (HbS) molecule leads to the polymerization of HbS, causing the blockage of microvasculature, oxidative stress, and endothelial damage. The clinical sequelae of SCD include vaso-occlusive crisis, hemolytic episodes, and end-organ damage. Obstructive sleep apnea (OSA) is a common but underdiagnosed condition associated with nocturnal hypoxemia due to intermittent upper airway closure. Repetitive episodes of hypoxemia can cause nocturnal sympathetic activation, selectively activate vascular inflammatory pathways leading to endothelial dysfunction, and can impact cardiac output to predispose patients to ischemia. The impact of this pathophysiology on SCD remains unclear and the literature reviews evaluating the relationship of SCD and OSA are scarce. METHODS We performed a retrospective analysis of the Nationwide Inpatient Sample data in adult patients (age greater than 18 years) hospitalized with SCD as the primary diagnosis in 2020 using ICD-10-CM codes. The NIS is the largest all-payer publicly accessible inpatient healthcare database in the United States. We compared the SCD cohort of 164,990 patients to another consisting of SCD with associated secondary diagnosis of OSA, which consisted of 32,998 patients. The Pearson chi-square test and Student's t test were used to assess categorical and continuous variables, respectively. RESULTS Data revealed that patients diagnosed with SCD and OSA had a statistically significant (p < 0.001) greater incidence of comorbidities compared to SCD alone. These included uncomplicated hypertension (29.8 vs 15.5%), complicated hypertension (24.5 vs 10.6%), uncomplicated diabetes mellitus (9.8 vs 3.4%), complicated diabetes mellitus (17.1 vs 5.1%), obesity (38.9 vs 9.2%), peripheral vascular disease (6.0 vs 3.2%), chronic pulmonary disease (39.7 vs 21.1%), chronic kidney disease (10.0 vs 4.1%), coronary artery disease (15.3 vs 5.1%), and heart failure (13.4 vs 5.4%). Illicit drug use was higher (8.4%) in SCD only compared to SCD with OSA (5.1%). CONCLUSION In this study, co-diagnoses of SCD and OSA revealed a greater likelihood of having other comorbidities, typically 2-3 fold. A striking finding is the increased prevalence of complicated hypertension and diabetes mellitus which are known to give way to vasculopathies, a sequela that is unfavorable in patients with SCD. Considering the clinical implications of these comorbidities and concern for overall underdiagnosis of OSA, it may prove beneficial to lower the threshold for OSA screening in patients with SCD who exhibit hypertension, diabetes, obesity, and other disease processes associated with OSA. Furthermore, should OSA screening in patients with SCD prove favorable, a prospective study evaluating outcomes, such as number of hospitalizations due to sickle cell crisis or acute chest syndrome, of patients diagnosed with OSA and subsequently treated with therapeutic measures such as nocturnal continuous positive airway pressure. Likewise, patients with established co-diagnosis of SCD and OSA should have diligent surveillance and treatment of these aforementioned comorbidities.

Is Epigenetic Modulation to Induce Fetal Hemoglobin Translatable in Sickle Cell Mice?

Sickle cell disease (SCD) is a genetic disorder caused by a mutation in the β-globin subunit of hemoglobin, resulting in the formation of HbS. Under deoxygenation, HbS polymerizes leading to red blood cell sickling, increased hemolysis and multi-organ damage. During human fetal development, due to expression of the γ-globin gene, the predominant type of hemoglobin produced is fetal hemoglobin (HbF). However, after birth, this shifts to adult globin (HbA or HbS in SCD). This is driven by epigenetic repression of γ-globin due to an increased methylation of its gene promoters. DNA methyltransferase 1 (DNMT1) is an important enzyme for DNA methylation and is known to be pivotal in regulation of HbF expression. Reactivation of HbF provides a functional hemoglobin, and therefore has the potential to treat SCD symptoms ( Steinberg et al. JAMA 2003;289:1645-51). HbF induction is an accepted treatment strategy in SCD; even small increases result in decreased vaso-occlusive crises and mortality ( Kato et al. Nat Rev Dis Primers 2018;4:18010). Decitabine inhibits DNMT1 activity, thus promoting γ-globin expression and thereby increasing HbF levels. While inhibition of DNA methylation is known to cause HbF induction in humans and non-human primates, the effects observed in SCD mouse models are more ambiguous. This study investigated to which extent decitabine treatment could induce HbF expression in the Townes SCD model. In Townes mice, the murine globin genes have been substituted for their sickle human counterparts, HBA, HBB sickle and HBG1, and mimic many features of human SCD. Mice aged 4-5 weeks were dosed subcutaneously 3 times a week for 12 weeks with research-grade decitabine (0.6 mg/kg or 0.4 mg/kg) or vehicle. Blood samples were collected for analysis of HbF protein levels by HPLC (represented as % of total Hb) and F-cells by flow cytometry (represented as % of the total RBC population positive for HbF), complete blood counts, histology, and other markers of disease and organ damage. Results are presented as mean ± SD. Groups were compared using an ANCOVA model, adjusting for multiple comparisons (Dunnett) with p<0.05 considered statistically significant. For both treatment groups, HbF was significantly elevated compared to the control group, with the maximal response observed at 12 weeks (Figure 1). F-cells at the end of the study were increased in both 0.4 mg/kg (11.4±1.5%) and 0.6 mg/kg (11.8±1.4%) groups compared to vehicle (4.5±0.6%). The same was observed for protein levels: 0.4 mg/kg group (1.2±0.3%), 0.6 mg/kg (1.4±0.3%) compared to vehicle (0.4±0.1%). Interestingly, after 12 weeks RBC and reticulocyte counts were significantly decreased in treatment groups and mean corpuscular volume (MCV) was significantly increased. No changes on LDH, bilirubin and liver markers (ALP, ALT, AST) were observed at 6 or 12 weeks. The results showed that treatment groups had significantly higher HbF levels than the vehicle group. However, the level of induction was lower than observed for inhibition of DNA methylation in humans and primates. The decrease in RBCs and reticulocytes could be partially explained by a combination of HbF induction, reduction of sickle RBC, and inhibition of erythropoiesis. The lack of changes in disease markers suggests that the increase in HbF levels in Townes mice might not be sufficient to alleviate the disease. This observation is consistent with recently published data (Woodard et al. Dis Model Mech. 2022;15(6)) that indicates that Townes mice are less suitable for studying this mechanism of action since, even though they have all human globin genes and some proximal regulatory elements, they lack key cis-acting distant DNA elements that regulate the globin genes. However, in primates the globin structure and regulation mechanisms are similar to human (Hardison. Cold Spring Harb Perspect Med. 2012;2(12)). In conclusion, although the measured levels of HbF protein were no higher than 2%, we found that decitabine can induce HbF expression in the Townes mouse model of SCD. However, within the 12-weeks, there was no clear beneficial effect on the disease markers studied. The successful induction of HbF suggests that better outcomes might be achieved with further optimization of the dosing and duration of the study. This indicates that SCD mice may be useful for preclinical studies of HbF induction, but caution is needed when extrapolating results to humans.

Management of Malignancies in Patients with Sickle Cell Disease

Background: In recent years, wider use of hydroxyurea has increased the average lifespan of individuals with sickle cell disease (SCD). With increased lifespan, recent reports suggest an increase in the risk of malignancy in SCD patients. Studies from California report a 72% increased risk of developing hematologic malignancies in patients with SCD compared to age, sex, and race matched controls. However, cancer-specific survival is similar to non-SCD patients. There are no guidelines for treatment considerations in the management of malignancies in patients with SCD. Therefore, we surveyed adult and pediatric SCD providers on their approaches to the management of cancer in patients with SCD. Herein we present preliminary data from the initial survey respondents. Methods: Adult and pediatric SCD providers were invited to participate in an electronically distributed REDCap survey. This survey contained 18 questions designed to determine practice preferences in the provider's approach to management of malignancies in patients with SCD, including the management of anemia, anticoagulation, and peri-operative considerations. The responses to each survey question were analyzed for trends, with responses summarized in counts, percentages, and corresponding 95% Clopper-Pearson confidence intervals (CI). Results: Among 47 providers that have completed the survey to date, 20 have managed patients with co-existing SCD and malignancies and were included in the analysis. In this provider group, which included both physicians and advanced practice providers, half [50% (CI 27.2-72.8)] care for 200-500 patients with SCD annually. The most common survey responses to selected questions are summarized in Table 1. Conclusion: Comprehensive care for patients over the last few decades has increased the lifespan of people living with SCD. This has resulted in an increased diagnosis of adult-onset cancers along with associated challenges in cancer management. Thus far, the survey responses have shown a trend that providers maintain a hemoglobin goal of 7 g/dL for transfusions, and the majority do not use erythropoietic stimulating agents for the management of anemia. Most providers reported not using G-CSF in post-chemotherapy neutropenic patients. When asked about primary thromboprophylaxis, responders said they do not routinely use the Khorana score for risk stratification or recommend surveillance imaging for venous thromboembolic events [VTE]. However, if the Khorana score is high or patients are on thrombogenic agents, providers recommend consideration of primary prophylactic anticoagulation. Providers also recommend close monitoring of renal function with the use of renally cleared chemotherapy agents. Multiple methods such as the use of Bair Huggers, warming blankets, warm IV fluids and avoidance of cell savers, tourniquets and intra-operative fluoroscopy were recommended to avoid peri-operative vaso-occlusive crisis. These data are limited currently, with insufficient responses to conduct larger analyses. Given the paucity of clinical data and the nuances associated with sickle cell specific risks, there may be reliance on expert opinion for the management of malignancies in patients with sickle cell disease.

20-HETE As an Emerging Target to Improve Renal Health in Sickle Cell Disease

The kidney is one of the most severely affected organs in sickle cell disease (SCD), with glomerular hyperfiltration and microalbuminuria beginning in childhood, and progressing to chronic kidney disease (CKD) in majority of adults. Sickle individuals also suffer from acute kidney injury (AKI) often during characteristic vaso-occlusive crisis. Renal pathology in sickle cell nephropathy includes extensive microvascular congestions and thrombotic microangiopathy. The hypercoagulable and vasoconstrictive environment of SCD, in conjunction with medullary hypoperfusion and cortical hyperperfusion contributes to vaso-occlusive injury and deregulates intrarenal hemostasis leading to CKD development. Ischemic injury increases arachidonic acid hydroxylation producing 20-hydroxyeicosatetraenoic acid (20-HETE), which in turn triggers thrombosis and promotes vasoconstriction in the kidney. However, the role of 20-HETE in regulating renal hemostasis in SCD nephropathy has never been reported. We found that plasma 20-HETE is significantly elevated in SCD patients (n=9-11; p<0.01) compared to normal individuals. Similarly, transgenic SCD mice (SS), homozygous for human hemoglobin S, have increased plasma 20-HETE compared to control mice (AA), homozygous for human hemoglobin A (n=6; p<0.01). We have previously shown that elevated circulating heme mimicking hemolytic crisis triggers clinically relevant acute kidney injury (AKI) in SS mice (Blood (2020) 135(13): 1044-1048). We postulated that hemolytic stress may exacerbate 20-HETE production which in turn aggravates renal microvascular occlusion and vasoconstriction, leading to renal damage in SCD. Immunohistochemistry and biochemical experiments showed that the expression of CYP4A12a, a cytochrome 450-dependent enzyme responsible 20-HETE production in mice, is substantially elevated in the kidneys of SS mice compared to AA mice, associated with increased vascular congestion and renal thrombogenesis. Renal CYP4A12a and plasma 20-HETE were increased substantially following heme-induced AKI in SS mice, associated with a heightened expression of renal angiotensin II receptor 1 (ATIIR1), thus indicating induced vasoconstrictive activity. In vitro, we found that 20-HETE induced ATIIR1 expression in human renal glomerular endothelial cells (hRGEC), which was further exacerbated by low-concentration of heme challenge (5 mM for 24 hour). Nitro-oleic acid (NO 2-OA) is a nitrated fatty acid that binds ATIIR1 and inhibits angiotensin II induced vasoconstriction. Pretreatment with NO 2-OA reduced 20-HETE-dependent ATIIR1 expression in hRGEC, while NO 2-OA prophylaxis during hemin-induced AKI inhibited albuminuria, normalized plasma creatinine levels, and lowered the expression of ATIIR1 in SS mice kidneys. Overall, our data show that elevated 20-HETE levels during hemolytic stress may aggravate renal injury in SCD which can be prevented by NO 2-OA prophylaxis. Ongoing experiments will determine the direct effect of elevated 20-HETE in renal hemostasis and CKD development in SCD.

Remote Blood Hemoglobin Monitoring with Hyperspectral Color Truthing for Advancing Sickle Cell Care

Introduction: An urgent need exists for a noninvasive telemedicine approach to alleviate the burdensome reliance on frequent invasive blood draws for monitoring blood hemoglobin (Hgb) levels in sickle cell disease (SCD) patients. SCD is the most common genetic blood disorder, impacting over 20 million people worldwide, resulting in frequent emergency healthcare use. A blood Hgb level is pivotal in managing SCD and understanding the pathophysiology of SCD including anemia. Even low blood Hgb levels may indicate painful vaso-occlusion crises (Blood 2021;137:2010). Thus, a remote noninvasive monitoring ability of blood Hgb in at-home settings can potentially enhance SCD management without iatrogenic blood loss. Advanced machine learning and spectroscopic analyses can enable digital colorimetric diagnostics for noninvasive blood Hgb quantification with high fidelity, empowering SCD patients. However, one of the key challenges in diagnostic photography is that clinical photos exhibit significant variations in colors, depending on devices, light conditions, and image file formats, hampering reliable colorimetric diagnostics. Methods: We have developed colorimetric analyses of peripheral tissue perfusion to offer remote monitoring and cost-effective blood Hgb readings for SCD patients. A specially designed diagnostic color reference chart, which is highly sensitive to blood Hgb and peripheral perfusion, allowed us to noninvasively predict blood Hgb levels from digital photos of the palpebral conjunctiva (inner eyelid) across diverse smartphone models, light conditions, and file formats. Specifically, a pilot human study of fifteen SCD patients aged 14 to 73 years generated 156 photos from both left and right eyelids juxtaposed with the diagnostic color reference chart, using Samsung Galaxy S21 and Apple iPhone 12 Pro, taken immediately before or after blood draws. Combining a blood Hgb computation (Optica 2020;7:563), blood Hgb levels were computed involving three primary machine learning algorithms (Figure 1): color recovery of the palpebral conjunctiva, hyperspectral learning to reconstruct a spectrum, and spectroscopic blood Hgb quantification. Results: Using our specially designed color chart (Figure 2a), the linear correlation between the computed blood Hgb levels and venous blood Hgb levels shows a high correlation coefficient of 0.88 and 0.81 for Samsung Galaxy S21 and Apple iPhone 12 Pro, respectively. The Bland-Altman plot as a non-parametric statistical method reveal that the 95% limits of agreement (95% LOA) are [-2.68, 2.10 g dL -1] and [-2.74, 3.19 g dL -1] for the two smartphone models. Conversely, when using a conventional color chart for general photography (Macbeth ColorChecker) (Figure 2b), the computed blood Hgb levels exhibit a low accuracy for both Samsung Galaxy S21 (correlation coefficient of 0.69, 95% LOA = [-5.05, 2.60 g dL -1]) and Apple iPhone 12 Pro (correlation coefficient of 0.57, 95% LOA = [-5.14, 5.87 g dL -1]). Conclusion: This study supports the feasibility of noninvasive blood Hgb assessments as colorimetric diagnostics for SCD patients in telemedical settings. The results correlate significantly with conventional laboratory tests based on venous blood draws and are highly comparable to capillary blood sampling (finger prick) tests (Respiratory Care 2019;64:1343). This study lays the foundation for realizing color accuracy in biological tissue for digital diagnostic colorimetric applications of blood Hgb.The proposed color accuracy-based digital health technology can potentially offer accessible, affordable, and reliable blood Hgb readings via smartphones in at-home or telemedicine settings.

Addressing Chronic Anemia in Sickle Cell Disease: Characterizing Erythropoiesis-Stimulating Agent (ESA) Utilization and Practice Patterns Among Providers

Background: Chronic anemia exerts profound impacts on the morbidity, mortality, and quality of life in individuals with sickle cell disease (SCD), but therapeutic options are limited. Erythropoietin-stimulating agents (ESAs) are the standard of care for managing anemia in chronic kidney disease (CKD). However, their utilization in SCD remains ad hoc, with limited literature and no guidelines supporting the use of ESAs in SCD. To address this knowledge gap, we present preliminary findings from a survey designed to evaluate provider practices and identify factors influencing the use of ESAs in SCD. Methods: We conducted a cross-sectional web-based survey from March-July 2023 among providers taking care of patients with SCD in the United States (US) and internationally. Survey items were developed to assess provider demographic characteristics, practice environments, and provider practices around ESA use in SCD. The data was collected and managed using REDCap electronic data capture tools hosted at the University of Pittsburgh. Descriptive statistics were used to report the data. Results: The survey has been completed by 33 providers as of a cut date of July 23, 2023. Most providers were hematologists who practiced in an academic setting (23/33, 69.7%), with an equal gender distribution (Table 1). The number of patients with SCD seen annually varied, with 101-300 patients being the most common cohort size (13/33, 39.4%). In the 12 months prior to survey completion, 15/33 (45.5%) providers treated at least 1 patient with SCD with ESAs, usually outpatient (Table 2). Commonly reported barriers to outpatient ESA therapy included lack of insurance approval/coverage or cost concerns, lack of provider experience, and patient tolerability/adherence or inability to perform self-injections. Fewer respondents reported no barriers to prescribing ESAs in the outpatient setting, compared to in the acute/inpatient setting (18.2% vs. 48.5%). The most commonly reported indications for starting ESAs in the outpatient setting were chronic anemia from end-stage renal disease or CKD, reduction of blood transfusion requirement, and chronic anemia in patients refractory to approved therapies. Less commonly reported indications include severe or symptomatic anemia alone and chronic anemia in the setting of cardiopulmonary disease. Respondents reported several contraindications to starting ESAs, including a history of venous thromboembolism (VTE), malignancy, stroke, coronary artery disease, hypertension, and frequent vaso-occlusive crises. Respondents also expressed concerns about the cost/insurance coverage, efficacy, safety, patient burden, and appropriate dosing of ESAs in patients with SCD. Only 18/33 (54.5%) respondents reported ever treating outpatients with SCD with ESAs; nearly all of them used 1 st generation ESAs, and a majority used 2 nd generation ESAs. For 1 st generation ESAs, the most common starting dose was 3500-7000 units (U) (50-100 U/kg; 22.2%) or 7001-14000 U (101-200 U/kg; 22.2 %). Once weekly was the most common dosing interval (50%), followed by three times a week (TIW; 27.8%) and twice a week (16.7%). The maximum dose used was 56001-70000 U (801-1000 U/kg) TIW. For 2 nd generation ESAs, the most common starting dose was 141-210 mcg (2.1-3.0 mcg/kg) (22.2%), and administration often occurred once every 2 weeks (44.4%) or weekly (27.8%). The maximum dose used was 211-315 mcg (3.1-4.5 mcg/kg) weekly. Outpatient ESAs were most often initiated for hemoglobin (Hb) < 6 g/dL (8/18, 44.4%), and Hb > 9 g/dL was the most common treatment target (6/18, 33.3%). ESAs were often combined with hydroxyurea, voxelotor, and simple transfusions (Table 2). Conclusion: These preliminary survey results show considerable variability in how ESAs are currently being used in people with SCD. These variations in clinical practice highlight both significant ambiguity about what works in this setting and the need for further research into the optimal use of ESAs for the management of chronic anemia in SCD (ongoing clinical trial: ACHiEvE-SCD, NCT05451940). Future directions include evaluating differences in practice patterns among adult vs. pediatric and US-based vs. non-US-based providers.

Vitamin D Deficiency and Avascular Necrosis in Patients with Sickle Cell Disease: A Retrospective Cohort Study

Introduction Sickle cell disease (SCD) is an inherited hemoglobinopathy with complex systemic involvement. Avascular necrosis (AVN) is a devastating complication among patients with SCD. Vitamin D deficiency (VDD) is commonly found in SCD patients, but there is limited research on the potential role of VDD as a risk factor for AVN in SCD patients. This study aimed to assess the association between VDD and AVN and determine the patterns, risk factors, diagnosis, and treatment of AVN in SCD patients. Methods We conducted a retrospective cohort study of consecutive SCD patients diagnosed with VDD from January 2020 to December 2022 at Prince Sultan Medical Military City (PSMMC) in Riyadh, Saudi Arabia. Patients meeting the following criteria were included: (1) adults and children with confirmed SCD through hemoglobin electrophoresis and (2) tested for VDD. Patients who underwent bone marrow transplant were excluded. The main outcome measured was the occurrence of AVN. VDD was diagnosed in patients with 25-hydroxyvitamin D levels below 30 nmol/L. Magnetic resonance imaging was used to stage and confirm AVN diagnosis. Associations were assessed using the chi-square test, and logistic regression was performed to control for confounding. Results The study included 711 eligible SCD patients, with 271 (38%) being children. VDD affected 301 out of 711 patients (42.3%). Among these, 212 (70.4%) were adults (>18 years old). VDD was observed in 32.2% of children and 48.1% of adults. Of the total cohort, 127 (17.9%) patients experienced AVN, including 18 children. Among patients with VDD, 89 developed AVN, while VDD affected 212 patients without AVN. The time between VDD diagnosis and AVN presentation ranged from 3 to 12 months. Male patients accounted for 52% of AVN cases. The average age at AVN diagnosis was 30.9 ± 11 years. The most common clinical presentation of AVN was chronic joint pain in over 95% of patients. Other presentations included limping in 3.9% of patients and limited joint movement in one patient. Affected joints included the hip (86%), shoulder (16.5%), knee (4.7%), and sacroiliac joint (0.7%). Bilateral joint involvement was present in 50.4% of AVN patients. The majority of patients (76.4%) were diagnosed with advanced stage AVN (III/IV). Treatment of patients with AVN included joint replacement in 44 (34.6%) patients, while the remaining 83 patients managed with conservative therapy such as pain control and physiotherapy. Patients with a history of VDD were significantly associated with a higher risk of AVN (p < 0.001), as seen in Table 1. Multivariate logistic regression showed SCD patients with VDD had 9.79 times the odds of AVN compared to SCD patients without VDD (OR 9.79; 95% CI: 5.25-18.26). Other statistically significant risk factors for AVN included frequent vaso-occlusive crises (three or more episodes per year), older age, history of acute chest syndrome, and low hemoglobin F levels. Conclusion AVN is a significant cause of morbidity in our SCD cohort, with most patients having advanced AVN disease. VDD is an independent risk factor for AVN in patients with SCD. Well-designed randomized trials are needed to determine the effect of vitamin D supplementation in reducing AVN in children and adults with SCD.

Initial Results in a Phase 1b Trial of PB-04 in Sickle Cell Disease Demonstrate Fetal Hemoglobin Induction, Additive Activity with Hydroxyurea, and Improved Red Blood Cell Sickling Parameters

Extensive evidence has shown fetal hemoglobin (HbF) is a major modulator of sickle cell disease (SCD) phenotype. Clinical benefit with any increment of HbF was shown in the NIH-sponsored Natural History Study and the Multicenter Study of Hydroxyurea (HU), with mean HbF increases of 3.6% above baseline (BL), to improve survival, reduce painful vaso-occlusive crises, and recently stroke prevention and improved cardiac and neurocognitive function with HU are reported. As some patients do not tolerate optimal HU doses due to cytopenias, additional inducers suitable for combined use are desirable. Proportions of F-cells and HbF-quantity/cell have been cited as important. PB-04, a repurposed drug with a well-known safety profile, is an oral fetal globin stimulant identified in high throughput screening, which suppresses 4 repressors of the HMG gene promoter, ( BCL-11A, LSD-1, HDAC-3, KLF-1). PB-04 induces fetal globin in nonhuman primates, transgenic mice, with additive effect when combined with HU in SCD erythroid progenitors, and was shown to reduce infarcts in multiple organs with preserved splenic function in transgenic sickle mice. An ongoing Phase 1b trial in beta thalassemia intermedia (BTI) ( NCT04432623) of 3 doses (1,3, or 5 mg/kg QD) given 3 (TIW) or 5 times/week (Wk) for 12 or 24 Wks in 18 courses in 10 subjects demonstrates a favorable safety profile, dose-proportional PK with 5 >3 mg/kg doses and 5 >3 doses/Wk, Median fold-increases from baseline (BL) in F-cells of 4.4x BL (range 2.3-7x), 2.8x F-reticulocytes (1.6-14.8x), and 6.5x (range 3-11x) increases in mean fluorescence intensity (MFI, representing amount of HbF/RBC). Mean increases in % HbF were 6.5%. Evaluation of PB-04 has now begun in 7 subjects with SCD, 19-51 yrs; 3 were receiving HU with HbF responses (12-22%). Adverse events, F-cells, F-reticulocytes, MFI (amount of HbF/RBC or HbF/reticulocyte) by FACS and ImageStream Analysis and % HbF are assessed Q 4 wks; flow adhesion of whole blood to VCAM-1 (FA-WB-VCAM) and sickling kinetics are assessed q 12 wks. In 4 subjects on 3 mg/kg QD TIW for 24 wks, changes observed from BL values included mean increases of 6% F-cells and 27% F-reticulocytes (2-fold) . In 3 ongoing subjects receiving 5 mg/kg QD TIW for 12 wks mean changes above BL are currently 13% F-cells, 15% F-reticulocytes; HbF/cell or HbF/reticulocyte have increased up to 10-fold. Mean % HbF has increased above HU effects in 2/3 pts on the second dose by 5-12.6% (mean 8.8%), producing 81-95% F-cells, and 35-38% HbF. Decline in FA-WB-VCAM) was observed ± HU and with both doses in 3 subjects. Correlation of HbF quantity/cell with RBC survival and sickling dynamics is being explored. These early results with not-yet-optimized doses of PB-04 suggest additive activity with HU, producing significant HbF and F-cell levels, and support further PK-optimized studies in patients with SCD.

Enhanced Expression of Heme Oxygenase-1 (HO-1) Among Children with Sickle Cell Disease: Results of the Sickle Cell Disease Genomics of Africa (SickleGenAfrica) Study

Sickle cell disease (SCD) is characterized by intense and chronic intravascular hemolysis that generates multiple erythroid danger associated molecular pattern (eDAMP) molecules in the extracellular space. Extracellular heme is a prototypical eDAMP that causes tissue injury and is associated with multiple complications of SCD including vaso-occlusive crisis, acute kidney injury and acute chest syndrome (ACS). Heme-oxygenase-1 (HO-1) is the rate-limiting enzyme that degrades heme to neutralize its deleterious effects on organ function. Raised extracellular heme is associated with 2.5 higher odds ratio of developing ACS, while HO-1 gene promoter allelic variants that drive robust HO-1 expression are associated with lower ACS-related hospitalization rates among children. Young transgenic homozygous SCD (SS) mice have higher survival rates than adult SS mice from a heme-induced ACS model due to their ability to rapidly degrade excess extracellular heme. While these data suggest that HO-1 may be involved in the well-established higher ACS survival among children, and potentially other ameliorating features of SCD in early development, no study had previously studied HO-1 expression in this patient population. The SickleGenAfrica Network enrolled over 2,000 children and adults with SCD from three sites in Ghana from 2018 to 2021, with consent for use of samples in future studies. The SCD status of participants was confirmed using automated capillary hemoglobin electrophoresis, and serum HO-1 level measured using ELISA. Patients were grouped based on age, using five-year intervals. The median HO-1 level comparisons across groups were performed using the pairwise Wilcoxon test, with Bonferroni correction for multiple comparisons. All analyses were performed using R version 4.3.1. The study included 1,971 patients with SCD, with a median age of 13 years (range 0 - 78), of which 1,067 participants (55%) were female. The majority of patients (1149 ;58%) had HbSS, 589 (30%) had HbSC, 171 (9%) sickle-hereditary persistence of fetal hemoglobin, and 62 (3%) HbS-beta(+). We observed an approximately 3-fold drop-off in median HO-1 levels between the 11-15-year-old (73.9 ng/ml) and 16-20-year-old (25.1 ng/ml) age groups (adj. p<0.001). Furthermore, males had higher average HO-1 levels (85.5 ng/ml) relative to females (63.1 ng/ml) (p<0.001). Our data show for the first time that children with SCD have significantly elevated HO-1 levels relative to adults, with a sharp decline in HO-1 levels during adolescence. HO-1 may serve as a protective SCD factor, contributing to enhanced ACS survival rates in children versus adults. To the best of our knowledge, this is the first study of HO-1 levels in patients with SCD at different ages. Our future work aims to establish whether baseline blood HO-1 levels can predict ACS incidence and severity, in addition to further investigating genetic and epigenetic mechanisms controlling HO-1 expression.

1307. Vaso-occlusive Crisis is Associated with Subsequent Osteomyelitis in Pediatric Sickle Cell Disease

Abstract Background Children with sickle cell disease (SCD) commonly develop microvascular infarcts of bone known as vaso-occlusive crisis (VOC) and are also at high risk of osteomyelitis (OM). VOC and OM can be challenging to distinguish due to overlapping clinical features. VOC might predispose to OM, or an initial misdiagnosis of OM as VOC might lead to delayed diagnosis of OM. This study aimed to test whether VOC was associated with subsequent development of OM in children with SCD. Methods A retrospective Pediatric Health Information System (PHIS) database study (2010-2021) was performed. ICD-code data related to common diagnoses in pediatric patients with SCD were extracted. The rate of VOC within 30 and 180 days preceding episodes of OM was compared to the rate preceding acute chest syndrome (ACS), another common diagnosis in children with SCD but unlikely to be anatomically related to OM. Odds ratios (OR) were used to evaluate the association between these diagnoses. Results Of 22,818 PHIS participants with SCD, 13,699; 450; and 7,327 had ≥ 1 episode of VOC, OM and ACS, respectively. The distribution of OM diagnoses was similar across pre-specified age groups (0-4, 5-12, and 13-18 years). The odds ratio of VOC preceding a diagnosis of OM vs. ACS was 2.15 within 30 days (95% CI: 1.82-2.54; p= 3.68 x 10-18), and within 180 days was 1.39 (95% CI: 1.20-1.62; p=2.04 x 10-5). VOC Preceding Osteomyelitis vs. Acute Chest Syndrome Conclusion VOC was significantly more common in the days preceding a diagnosis of OM than of ACS. The strength of association was stronger within 30 days prior to OM than 180 days. These results suggest possible misdiagnosis of OM since VOC might delay OM diagnosis in some cases, that recurrent VOC might be misdiagnosed as OM, or that VOC can directly contribute to risk of OM in some cases. Limitations of this study include possible incomplete adjustment for unmeasured variables which could confound the analysis. More research is needed to confirm and evaluate the mechanism behind this association. Understanding the relationship could lead to improved screening and treatment of both VOC and OM. Disclosures Joshua Wolf, MBBS, PhD, Karius Inc.: Grant/Research Support|Merck Inc.: Participation in industry-sponsored research Sandra Arnold, MD, Contrafect: Grant/Research Support|Enanta: Grant/Research Support|Moderna: Grant/Research Support|Pfizer: Grant/Research Support

Use of Disease-Modifying Treatments in Patients With Sickle Cell Disease

Despite hydroxyurea being an established treatment for sickle cell disease (SCD), it remains underused. The recent approval of the disease-modifying treatments (DMTs) l-glutamine, crizanlizumab, and voxelotor underscores the need to understand the uptake of DMTs in the current treatment landscape. To explore characteristics that may be associated with DMT use and to describe observed patterns of yearly DMT use from 2014 to 2021. This cross-sectional study used administrative claims data from Optum's deidentified Clinformatics Data Mart Database from January 1, 2014, to September 30, 2021, to identify adults and children with SCD. Data were analyzed from August 1, 2022, to August 28, 2023. Use of DMTs. Patient characteristics across groups with varying patterns of DMT use and yearly patterns of prescription fills for hydroxyurea, crizanlizumab, voxelotor, and l-glutamine. A total of 5022 beneficiaries with SCD (2081 [41.4%] aged 18-45 years; 2929 [58.3%] female) were included in sample A (144 [2.9%] inconsistent users, 274 [5.5%] incident users, 892 [17.8%] consistent users, and 3712 [73.9%] non-DMT users). Inconsistent users had a higher prevalence of vaso-occlusive crises (mean [SD], 3.7 [4.7]), splenic complications (6 of 144 [4.2%]), pulmonary complications (36 of 144 [25.0%]), kidney disease (21 of 144 [14.6%]), acute chest syndrome (18 of 144 [12.5%]), and health care visits (eg, mean [SD] inpatient visits, 7.0 [10.7]) compared with the other use groups. Non-DMT users had the lowest prevalence of vaso-occlusive crises (mean [SD], 0.8 [2.4]), acute chest syndrome (109 of 3712 [2.9%]), and inpatient (mean [SD], 2.0 [6.6]) and emergency department (mean [SD], 0.7 [3.1]) visits and the highest proportion of adults 65 years and older (593 of 3712 [16.0%]). In sample B (6387 beneficiaries with SCD), hydroxyurea use modestly increased from 428 of 2188 participants (19.6%) in 2014 to 701 of 2880 (24.3%) in 2021. Use of l-glutamine increased briefly but gradually decreased throughout the study period. In 2021, out of 2880 participants, 102 (3.5%) had at least 1 fill for crizanlizumab and 131 (4.6%) had at least 1 fill for voxelotor. Overall, total DMT use increased from 428 of 2188 participants (19.6%) in 2014 to 815 of 2880 patients (28.3%) in 2021. In this cross-sectional analysis of adults and children with SCD, uptake of DMTs remained low from 2014 to 2021, despite the approval of newer therapies. Notable differences in patient characteristics across varied DMT exposure types necessitate further exploration into factors that facilitate DMT use and the creation of strategies to enhance DMT uptake.

Comparison of in-hospital mortality in children and adolescents with sickle cell disease in a resource-limited setting before and during the COVID-19 pandemic

BackgroundCOVID-19 in children and adolescents with sickle cell disease (SCD) has variable presentations (from mild to severe disease), and the main symptoms are vaso-occlusive crises (VOC) and acute chest syndrome (ACS). We hypothesized that the desertion of hospitals due to the pandemic would lead to late arrival at the emergency room and an increased mortality. In this study, we sought to measure and compare the mortality of children with sickle cell disease before and during the COVID-19 pandemic. Material and methodsWe conducted a retrospective cohort study at the sickle cell disease management center of Laquintinie Hospital in Douala (Cameroon). The study period was divided into two, i.e., from March 2019 to February 2020 (Pre-COVID-19) and from March 2020 to February 2021 (COVID-19). All administrative and ethical considerations were fully respected. Data were analyzed using SPSS 20.0. ResultsOverall, 823 patients were admitted during the study period. Males represented 52.4% of the overall population, giving a sex ratio of 1.1:1. We admitted 479 patients during the pre-COVID-19 period versus 344 patients during the COVID-19 period, which is a 28.2% drop in admissions during the COVID-19 period. The mortality rate was 3.5% during the pre-COVID-19 period and 3.2% during the COVID-19 period (p>0.05). The most common causes of death were ACS (39.3%, n = 11), severe anemia (25.0%, n = 7), and VOC (17.9%, n = 5). ACS (adjusted odds ratio [aOR]=3.628, 95% confidence interval [CI], [1.645–7.005], p<0.001) was significantly associated with mortality. ConclusionDuring the COVID-19 pandemic, although the consultation frequency decreased, the mortality rate of sickle cell disease patients remained unchanged.