Function In Sickle Cell Disease Research Articles

Assessment of Neurocognitive Functioning in Sickle Cell Disease and Thalassemia and the Association with Silent Cerebral Infarcts and Cerebral Hemodynamics and Oxygen Metabolism

Introduction Neurocognitive impairment is a significant problem in patients with sickle cell disease (SCD), affecting various life domains such as academic achievement, career progress, and general life quality. The cause of this impairment is not yet fully understood, however, it has been linked to silent cerebral infarcts (SCIs) and irregularities in blood perfusion and oxygenation, particularly in children with SCD. Previous research has identified cognitive deficits in adults with SCD, but the relationship with SCIs has not been thoroughly explored in this age group. This study aimed to examine the neurocognitive functioning among adult patients with three types of inherited chronic anemia (severe SCD, mild SCD, and thalassemia) and healthy controls. Additionally, we investigated potential associations of neurocognitive performance with cerebral perfusion and oxygenation, and SCIs. Methods This study included 70 severe SCD patients (60 HbSS, 10 HbSβ 0), 22 mild SCD patients (14 HbSC, 8 HbSβ +), 16 thalassemia patients (6 NTDT, 10 TDT), and 29 healthy controls. We assessed neurocognitive functioning through eight tasks divided into seven neurocognitive domains such as attention, processing speed, nonverbal IQ, working memory, verbal learning, visual memory, and fine motor dexterity. Each task score was standardized using published norm data, converted into Z-scores, and used to compute the mean Z-score per domain. SCIs were assessed and segmented using FLAIR MRI scans. Cerebral blood flow (CBF) and oxygen extraction fraction (OEF) were derived using time-encoded pseudo-continuous arterial spin labeling (te-pCASL) and T 2-relaxation-under-spin-tagging (TRUST) techniques, respectively. Cerebral metabolic rate of oxygen (CMRO 2) was calculated from the CBF, OEF and oxygen content (calculated from hemoglobin and arterial saturation). One-sample t-tests or one-sample Wilcoxon-signed rank tests were used to compare the seven neurocognitive domains of each group with normative test data and ANOVA was used to compare these domains between participant groups. Independent-sample t-tests or Mann-Whitney U tests were used to compare the neurocognitive domains between patients with and without SCIs. Lastly, correlation analyses explored the relationships between the neurocognitive domains and SCI volume, CBF, OEF, and CMRO 2. Results In the severe SCD group, only processing speed and fine motor dexterity were significantly impaired after adjusting for multiple comparisons (Table 1 & Figure 1). Mild SCD patients exhibited lower scores in processing speed, working memory, and fine motor dexterity compared to the norms. In contrast, after adjustment for multiple comparisons, thalassemia patients and healthy controls only showed significantly lower scores in fine motor dexterity (Table 1). When comparing groups, SCD patients had significantly slower processing speed compared to thalassemia patients and healthy controls. Surprisingly, SCD patients without SCIs exhibited poorer fine motor dexterity than those with SCIs (p=0.03), while no such associations were identified in other groups. Finally, no associations were found between the neurocognitive domains and SCI volumes, CBF, OEF and CMRO 2. Conclusion Our results show slower processing speed in SCD patients compared to thalassemia patients and healthy controls, aligning with previous studies. However, unlike previous research, we did not find additional neurocognitive deficits in SCD patients. This could be due to variations in patient selection, environmental factors, socioeconomic status, or recent enhancements in SCD treatment approaches, such as the early administration of hydroxyurea and/or blood transfusion. Interestingly, all groups showed diminished fine motor dexterity, potentially due to the ongoing digital transition. A key observation from this study was the lack of association between neurocognitive performance and SCIs, hemodynamics, and oxygen metabolism, suggesting that SCIs and oxygenation might not be the only factors contributing to impaired processing speed. Our results suggest that recent developments in medical treatments could have improved the neurocognitive function of SCD patients residing in Western countries. However, concerning the domain of processing speed, further studies are required to investigate other SCD-related factors that might influence this particular area.

Structural connectivity mediates the relationship between blood oxygenation and cognitive function in sickle cell anemia.

In sickle cell disease, the relative importance of reduced hemoglobin (Hb) and peripheral oxygen saturation on brain structure remains uncertain. We applied graph-theoretical analysis to diffusion magnetic resonance imaging data to investigate the effect of structural brain connectivity on cognitive function, alongside the presence or absence, number, and volume of silent cerebral infarction. In patients, we investigated the relationships between network properties, blood oxygenation, and cognition (working memory and processing speed indices). Based on streamline counts and fractional anisotropy, we identified a subnetwork with weakened connectivity in 92 patients with sickle cell disease (91 homozygous for HbS [HbSS], 1 heterozygote with HbSβ0 thalassemia; 49 males; aged 8.0 to 38.8 y), compared with 54 control subjects (22 males; aged 6.7 to 30.6 y). Multiple regression analyses showed a significant effect of Hb on full-network edge density (P< .05) and of peripheral oxygen saturation on streamline-weighted subnetwork efficiency (P< .01). There were effects of fractional anisotropy-weighted full-network and subnetwork efficiency on working memory index (both P< .05), and of streamline-weighted subnetwork efficiency on processing speed index (P= .05). However, there were no effects of presence, number or volume of silent cerebral infarcts. Streamline-weighted efficiency was progressively lower with lower oxygen saturation, with a downstream effect on the processing speed index. In path analysis, indirect relationships between blood oxygenation and cognition, mediated by network properties, were better supported than direct alternatives, with an indirect relationship between low oxygen saturation and processing speed index in patients, mediated by structural connectivity efficiency in a subnetwork of the brain differing from control subjects. Our findings are consistent with the notion that cognitive impairment is primarily mediated by hypoxic-ischemic effects on normal-appearing white matter and highlight the utility of network-based methods in providing biomarkers of cognitive dysfunction in patients with sickle cell disease.

Neuroimaging and Cognitive Function in Sickle Cell Disease: A Systematic Review.

Sickle cell disease (SCD) is the most common inherited single-gene disease. Complications include chronic anaemia, reduced oxygen-carrying capability, and cerebral vasculopathy, resulting in silent cerebral infarction, stroke, and cognitive dysfunction with impairments in measures of executive function, attention, reasoning, language, memory, and IQ. This systematic review aims to investigate the association between neuroimaging findings and cognition in children with SCD. Searches of PubMed and Embase were conducted in March 2022. Studies were included if participants were <18 years, if original data were published in English between 1960 and 2022, if any genotype of SCD was included, and if the relationship between cognition and neuroimaging was examined. Exclusion criteria included case studies, editorials, and reviews. Quality was assessed using the Critical Appraisal Skills Programme Case Control Checklist. A total of 303 articles were retrieved; 33 met the eligibility criteria. The presence of overt or silent strokes, elevated blood flow velocities, abnormal functional connectivity, and decreased fMRI activation were associated with neuropsychological deficits in children with SCD when compared to controls. There is a critical need to address the disease manifestations of SCD early, as damage appears to begin at a young age. Most studies were cross-sectional, restricting the interpretation of the directionality of relationships. Future research employing longitudinal neuroimaging and neuropsychological assessments could improve our understanding of the cumulative consequences of SCD on the developing brain.

Evaluating Equations for Estimated Glomerular Filtration Rate (eGFR) in Patients with Sickle Cell Disease (SCD)

Background: Assessment of kidney function in sickle cell disease poses a unique dilemma, both due to the presence of hyperfiltration and the increased tubular secretion of creatinine, the metabolite most often used in eGFR assessment. In the general population, formulae utilizing serum creatinine have been developed to estimate GFR. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) have developed the most recent formulae. Until recently, the CKD-EPI-2009 creatinine-based formula has been the standard for estimating eGFR and included black race as a variable in the formula. This formula has been noted to overestimate eGFR in SCD patients, but its bias is improved when the black race variable is excluded. Among available formulae, the CKD-EPI-2012 cystatin C-based formula was shown to have the least bias in SCD patients compared to radionucleotide measured GFR but loses its accuracy when combined with creatinine. The recently developed CKD-EPI-2021 formula which excludes race as a variable is becoming the standard formula in most clinical laboratories. In this multicenter study, we sought to evaluate the agreement of various CKD-EPI formulae in SCD patents. Methods: Patients with HbSS or HbSb0 thalassemia between ages 18 and 65 years were enrolled in a prospective cohort study to assess the natural history of kidney disease in SCD. We excluded patients with bone marrow transplantation, diabetic nephropathy, cancer, connective tissue disease, other glomerular diseases, known infection with hepatitis (B or C) or HIV, and end-stage kidney disease on dialysis. Participants were enrolled during routine clinical visits at four centers. At baseline, blood samples and urine were obtained, and kidney function was assessed using each sites clinical laboratory to measure serum creatinine. Serum cystatin C was also measured at baseline using a commercially available ELISA kit. We calculated eGFR using each of the CKD-EPI formula, excluding the race variable in the CKD-EPI-2009 formula. Spearman's rank correlation coefficients were calculated for each formula compared to the others. Prevalence of CKD was assessed using the CKD-EPI-2009, CKD-EPI-2012 (cystatin C) and CKD-EPI-2021 formulae and defined as the presence of albuminuria or an eGFR ≤ 90 ml/min/1.73m2. Prevalence of CKD derived from the CKD-EPI-2012 was compared to the other two formulae using McNemar's Chi-squared test with 95% confidence intervals determined using bootstrap replications. Results: Our cohort enrolled 284 subjects with HbSS or HbSb0 thalassemia. For these analyses, 277 patients with baseline serum creatinine were included. The mean age of included subjects was 32.9 (SD ±11.5) years and 57% were female (N=158). The median eGFR of these subjects using the creatinine-based CKD-EPI-2009 formula was 123.9 (IQR 105.9, 134.0) ml/min/1.73m2. Cystatin C was available in 270 patients and had median value of 0.72 (IQR 0.59, 0.92) mg/L. Correlation between the several eGFR formulae are presented in Table 1. CKD-EPI-2009 and CKD-EPI-2021 creatinine-based formulae were very highly correlated with each other; both had similar but less correlation with the CKD-EPI-2012 cystatin C-based formula, which has been shown previously to have the least bias when compared to measured GFR. The prevalence of CKD using the creatinine-based CKD-EPI-2009 formula was 51.3% and 50.5% using the creatinine-based CKD-EPI-2021 formula. When assessed with the cystatin C-based CKD-EPI-2012 formula, CKD prevalence was higher at 55.7% (p<0.0001) than that seen with both of creatinine-based CKD-EPI formulae. Conclusions: When comparing the new CKD-EPI-2021 creatinine-based formula to the CKD-EPI-2009 formula (excluding the black race variable), eGFR calculation remains very similar in SCD patients. The CKD-EPI-2009 formula is well recognized to overestimate eGFR in SCD patients. Our data would suggest the newer formula would have similar bias. Using the cystatin C-based CKD-EPI-2012 formula, the prevalence of CKD is higher in this SCD cohort than using creatinine-based CKD-EPI formulae, although our data are limited by lack of directly measured GFR. We anticipate the newer CKD-EPI-2021 creatinine-based formula would similarly underestimate prevalence of CKD in SCD. Use of cystatin C for assessing kidney function in SCD patients should be considered, and resources should be utilized to make this measure more widely and readily available. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

An Endogenous Metabolic Modulator Composition Improves Hydration Status and Decreases Adhesion Properties of Red Blood Cells from Patients with Sickle Cell Disease

Background Sickle cell disease (SCD) is a group of hemoglobinopathies caused by point mutations in the β-globin gene leading to abnormal red blood cells (RBCs). There are various forms of SCD; sickle cell anemia (SCA) is characterized by homozygosity for hemoglobin (Hb) S (HbSS) whereas HbSC disease results from compound heterozygosity for HbS and HbC. HbC does not lead to RBC sickling, but induces loss of intracellular K+ and H2O causing RBC dehydration. Similarly, in HbSS RBCs, through dehydration, an increase of the intracellular concentration of poorly soluble HbS enhances polymerization upon deoxygenation, causing RBCs to become rigid and to sickle. Until recently, the only approved therapy for SCD was hydroxyurea (HU). HU increases fetal Hb (HbF) levels and improves RBC hydration and deformability. For decades, amino acids have been explored as potential treatment to restore the disrupted pathophysiological pathways in SCD. RCitNacQCarLKHVS, an Endogenous Metabolic Modulator (EMM) composition of ten different amino acids and derivatives, was designed to target and support RBC metabolism. In this study, we investigated the effect of ex vivo treatment of this EMM on RBC properties and function in SCA and HbSC. Methods Blood of 12 different adult SCD patients (9 HbSS [of whom 6 were on chronic RBC exchange (RBCX)], 3 HbSC) and 2 healthy controls was collected. Whole blood was incubated at standardized hematocrit (20%, patient plasma) in the presence or absence of different RCitNacQCarLKHVS concentrations for 4h at 37°C. Routine hematological parameters were measured using the Cell-Dyn Sapphire (Abbott Diagnostics). Percentage of total dense RBCs (%DRBCs) was analyzed from 10/12 patients (4 HbSS on RBCX, 3 HbSS not on RBCX, 3 HbSC) using the Advia 120/2120 hematology analyzer (Siemens Healthcare Diagnostics). Point of sickling (PoS), RBC deformability (EImax), and hydration status (Ohyper) were assessed by oxygen gradient ektacytometry and osmotic gradient ektacytometry, respectively, in 12/12 patients using the Lorrca (RR Mechatronics). Blood viscosity was measured in 6/12 patients (3 HbSS not on RBCX and 3 HbSC) at 37°C using a cone-plate viscometer (Brookfield). The hematocrit-to-viscosity ratio (HVR) was calculated as follows: hematocrit/blood viscosity at 300 s-1. RBC adhesion to laminin (BioLamina) was assessed in 4/12 patients (3 HbSS not on RBCX, 1 HbSC) using a microfluidic device (IBIDI μ-Slide VI 0.4). Statistical analysis was performed in Graphpad Prism v9.3.0 using the Friedman test. Results Ex vivo treatment of blood of SCD patients with RCitNacQCarLKHVS showed a significant dose-dependent increase in Ohyper as measured by osmotic gradient ektacytometry (Figure 1), indicating an improvement of RBC hydration status of SCD RBCs. This was accompanied by a significant increase in mean corpuscular volume (MCV) and reduction in mean corpuscular Hb concentration (MCHC). RBCs of healthy controls showed a similar trend in Ohyper, MCV and MCHC. In addition, %DRBCs showed a significant dose-dependent decrease in both HbSS and HbSC RBCs as a result of RCitNacQCarLKHVS treatment. Oxygen gradient ektacytometry showed a significant increase in maximum deformability (EImax), but no significant change in point of sickling. The HVR did not significantly change during dose-response experiments. Median RBC adhesion to laminin decreased as a result of ex vivo treatment with RCitNacQCarLKHVS (Figure 2). Conclusion Ex vivo treatment with RCitNacQCarLKHVS demonstrated a significant dose-dependent increase in RBC hydration (Ohyper, MCV, MCHC and %DRBCs), deformability (EImax) and decreased adhesion properties in SCD RBCs. Dehydrated and dense RBCs with reduced deformability and increased adhesion are more prone to hemolysis, and associated with vaso-occlusive complications such as priapism, skin ulcers, and nephropathy. Results from this study therefore suggest benefit of EMM in modulating clinically-relevant rheological properties such as hydration state and adhesion of SCD RBCs in both SCA and HbSC. The fact that HVR did not change may represent an additional therapeutic benefit, especially for HbSC patients who have, in general, higher blood viscosity compared to HbSS patients. Moreover, it would be worthwhile to investigate if the concomitant use of select amino acid combinations with HU or other anti-sickling agents has an additional beneficial effect in SCD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Automating Pitted Red Blood Cell Counts Using Deep Neural Network Analysis: A New Method for Measuring Splenic Function in Sickle Cell Anaemia.

The spleen plays an important role in the body’s defence against bacterial infections. Measuring splenic function is of interest in multiple conditions, including sickle cell anaemia (SCA), where spleen injury occurs early in life. Unfortunately, there is no direct and simple way of measuring splenic function, and it is rarely assessed in clinical or research settings. Manual counts of pitted red blood cells (RBCs) observed with differential interference contrast (DIC) microscopy is a well-validated surrogate biomarker of splenic function. The method, however, is both user-dependent and laborious. In this study, we propose a new automated workflow for counting pitted RBCs using deep neural network analysis. Secondly, we assess the durability of fixed RBCs for pitted RBC counts over time. We included samples from 48 children with SCA and 10 healthy controls. Cells were fixed in paraformaldehyde and examined using an oil-immersion objective, and microscopy images were recorded with a DIC setup. Manual pitted RBC counts were performed by examining a minimum of 500 RBCs for pits, expressing the proportion of pitted RBCs as a percentage (%PIT). Automated pitted RBC counts were generated by first segmenting DIC images using a Zeiss Intellesis deep learning model, recognising and segmenting cells and pits from background. Subsequently, segmented images were analysed using a small ImageJ macro language script. Selected samples were stored for 24 months, and manual pitted RBC counts performed at various time points. When comparing manual and automated pitted RBC counts, we found the two methods to yield comparable results. Although variability between the measurements increased with higher %PIT, this did not change the diagnosis of asplenia. Furthermore, we found no significant changes in %PIT after storing samples for up to 24 months and under varying temperatures and light exposures. We have shown that automated pitted RBC counts, produced using deep neural network analysis, are comparable to manual counts, and that fixed samples can be stored for long periods of time without affecting the %PIT. Automating pitted RBC counts makes the method less time consuming and results comparable across laboratories.

Study of Prevalance of Nephropathy among Sickle Cell Disease Patients in Waghodia Region, Vadodara, Gujarat

Introduction: Sickle-cell disease (or drepanocytosis) is a life-long blood disorder Characterized by red blood cells that assume an abnormal, rigid, sickle shape. Sickle cell disease (SCD) has several complications, including chronic renal failure, manifesting with hypertension (high blood pressure) proteinuria (protein loss in the urine), hematuria (redblood cells in urine) and worsening anaemia. Progression to end-stage renal failure confers a poor prognosis.&#x0D; Objective: The objective of the study was to determine the Prevalence of Nephropathy among sickle cell disease patients.&#x0D; Materials and Methods: This cross sectional study includes a total 150 participants who suffering from sickle cell anemia and attending our Institute. Renal function test and Urine examination of all participants was done. Estimated Glomerular Filtration Rate (eGFR) calculated using the Cockroft Gault formula. Comparison of results was done between Sickle cell trait and Sickle cell disease Group.&#x0D; Results: The mean age of the SCA patients were 25.54±10 years. Maximum participants are found to be from age group 25-30 yr(n=35) followed by 20-25 yr(n=30). Of the 150 SCA patients, 89 (59.33%), and 61 (40.66%) were males and females, respectively. The Mean value of S.Creatinine of SCT group is 0.73±0.46 mg/dl and SCD is 1.0±0.35 mg/dl, while the Mean value of eGFR is 134.19±87.21 ml/min and 124.20 ±58.25 ml/min in SCT and SCD Group respectively.&#x0D; Conclusions: From our study we conclude that the Derangement of Kidney function in sickle cell disease is frequent in our setting especially among young adult. It concerns SCD as well as SCT patients. Albuminuria is more frequent in homozygote patients and its prevalence increase with age. Age ≥ 25 years is associated with high risk of CKD in SCA group and albuminuria in SCD.

Cerebral Blood Flow, Brain Volume, and Age Predicts Executive Function in Sickle Cell Anemia

Introduction: Individuals with sickle cell anemia (SCA) are at increased risk for deficits in multiple domains of neurocognitive functioning, including executive functions. In addition to assessing the effects of silent cerebral infarcts (SCI) and stroke on cognition, prior research has focused on hemoglobin and transcranial Doppler velocity as hemodynamic correlates. Recent studies have begun to use more precise measures of blood delivery to the brain (e.g., cerebral blood flow; CBF) to determine more sensitive indicators of cognitive risk prior to neurological injury. Nevertheless, empirical and meta-analytic findings suggest that these deficits increase with age, which can have broad impact on psychosocial functioning, including self-management and navigation through the transition from pediatric to adult medical care. This study aimed to assess brain volume as a mediator of the association between CBF and executive functioning in a sample of individuals with SCA. The secondary aim was to assess age as a moderator of hemodynamic and structural correlates of executive function.Methods: Children, adolescents, and young adults with SCA were enrolled prospectively. Each participant received a 3-Tesla non-contrast magnetic resonance imaging and magnetic resonance angiography of the brain, and a neurological examination by the study neurologist. Gray matter CBF was calculated from pseudo-continuous arterial spin labeling using the solution to the flow-modified Bloch equation after correcting for individual hematocrit. Three measures of brain volume were also computed from 3D-T1 images using Freesurfer version 7.1.1: total brain volume, gray matter volume, and white matter volume was calculated as the difference between the two. At a separate study visit, participants completed an age-appropriate Wechsler Working Memory Index (WMI). Pearson correlations assessed bivariate associations among variables, SPSS PROCESS macro was used to test gray matter volume as a mediator in the relation between CBF and working memory, and multiple linear regression analyses tested age as a moderator of the impact of CBF and brain volume on working memory.Results: Twenty-nine children and adolescents (ages 6 to 17 years) and 25 adults (ages 18 to 31 years) were enrolled. Five participants were excluded from analyses due to history of overt stroke that resulted in significant brain volume loss. Of 49 included participants, 20 had SCIs. Working memory was inversely correlated with age (r = -.30, p = .037) and CBF (r = -.36, p = .013), such that WMI decreased cross-sectionally with older age and higher CBF. Working memory was positively correlated with gray matter volume (r = .42, p = .002); however, it was not related to white matter volume (r = -.05, p = .715) or total brain volume (r = -.07, p = .642). Finally, patient age was positively correlated with CBF (r = .36, p = .014), but the association of age with gray matter volume did not reach statistical significance (r = -.27, p = .065). Analyses in Figure 1 show that although CBF and gray matter were directly related to working memory (path c and path b, respectively), gray matter volume did not mediate the association between CBF and working memory (path a*b). However, regression analyses (Table 1) showed that age moderated the association between gray matter volume and working memory, such that there was only a significant relation in children and adolescents. This association did not exist for young adults (Figure 2).Conclusions: Neurocognitive assessments has been cited as an important standard of care for children and adolescents with SCA. Given the increase in deficits with age, and the increase in mortality after transferring from pediatric to adult care, monitoring executive function abilities and potential impact on self-management should continue into adulthood. Findings from the current study provide preliminary evidence that cerebral hemodynamic compensation with elevated CBF may be insufficient to prevent gray matter volume loss in children and adolescents and decline in working memory ability. Some limitations of the current study include small sample size and whole brain gray and white matter volumes as opposed to specific regions relevant to executive functions (e.g., prefrontal cortex); however, findings from global measures provide promising evidence for future research on hemodynamic and structural predictors of executive function in SCA. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Social Determinants of Health and Neurocognitive Functioning in Sickle Cell Disease

Sickle cell disease (SCD) is associated with significant neurocognitive risk due to a combination of disease and environmental factors. Neurological complications, including overt stroke, silent cerebral infarctions, and chronic insufficiencies in oxygen and/or glucose delivery to the brain contribute to neurocognitive decline. Environmentally, patients with SCD experience greater rates of poverty and fewer protective socioeconomic factors when compared with the Black population in the United States. Both personalized (e.g. familial education and occupation) and community measures of socioeconomic status uniquely contribute to neurocognitive outcomes. However, no studies have examined the specific community-level factors that contribute to neurocognitive performance. The primary objective of this study was to investigate associations between familial and community-level social determinants with cognitive and academic outcomes in a large prospectively recruited sample of patients with SCD ranging from childhood to young adulthood.We included 103 patients with SCD (51% HbSS/HbSβ 0-thalassemia). The mean age of participants was 12.86 (SD=4.04) years. Familial socioeconomic status was measured using the Barratt Simplified Measure of Social Status (BSMSS), a composite of parent education and occupation status. Community-level (based on census block) socioeconomic variables included: poverty rate, unemployment rate, percentage of individuals with a bachelor's degree, and access to food nutrition services. Following informed consent, patients completed gold-standard neurocognitive measures supervised by a psychologist, assessing intellectual (Wechsler Abbreviated Scale of Intelligence - Second Edition) and academic functioning (Woodcock Johnson Tests of Achievement - Third Edition). Multivariate linear regression was used to examine associations between community and familial level socioeconomic status with cognitive/academic outcomes after adjusting for age, sickle genotype, and hydroxyurea exposure. Stepwise linear regression was used to identify the independent factors associated with cognitive/academic outcomes. The False discovery rate (FDR) developed by Benjamini and Hochberg was used to control for multiple testing and FDR-adjusted p-values (pFDR) <0.05 were considered statistically significant. Otherwise, p-values <0.05 were considered significant.Patients with SCD lived in communities with high rates of poverty (26.57%) and unemployment (13.58%) and low rates of college education (13.26%). In multivariate analyses adjusting for age, sickle genotype, and hydroxyurea exposure, IQ was associated with the BSMSS (estimate = 0.31, standard error [SE] = 0.10, p=0.003) at pFDR<0.05 but measures of basic reading and math were not (all pFDR>0.05).In contrast, reduced intellectual functioning was associated with increased poverty rates (Estimate=-0.29, SE=0.09, p=0.003), increased unemployment rates (estimate=-0.43, SE=0.18, p=0.018), increased access to food nutrition services (Estimate=-0.21, SE=0.09, p=0.015), and decreased percentage of individuals with a bachelor's degree (Estimate=0.33, SE=0.10, p=0.003) at pFDR<0.05. Measures of basic reading and math were not associated with any of the community-level variables. Stepwise linear regression analysis showed that the BSMSS (Estimate=0.22, SE=0.11, p=0.04) and poverty rates (Estimate=-0.18, SE=0.09, p=0.049) are independently associated with full scale IQ after adjusting for age, sickle genotype and hydroxyurea exposure. Overall, community and familial socioeconomic factors accounted for greater variance in intellectual functioning than age, genotype, and hydroxyurea treatment exposure (see Figure 1).Social determinants at the community-level contribute to intellectual development in patients with SCD independent of familial socioeconomic status. Surprisingly, academic performance was not associated with community-level social determinants. Evaluation of community-level social determinants may provide insights into potential targets for neurodevelopmental interventions. [Display omitted] DisclosuresEstepp: Global Blood Therapeutics: Consultancy, Research Funding. Hankins: Bluebird Bio: Consultancy; UpToDate: Consultancy; Global Blood Therapeutics: Consultancy; Vindico Medical Education: Consultancy.

Improved Hemolytic Anemia with GBT1118 Is Reno-Protective in Transgenic Sickle Mice

Intravascular hemolysis releases cell-free hemoglobin and heme into the circulation. When haptoglobin and hemopexin are depleted, as observed in sickle cell anemia, cell-free hemoglobin and heme can cause direct oxidative injury, upregulation of inflammatory and immune response pathways, and depletion of nitric oxide. The kidneys are the primary route for clearance of non-scavenged cell-free hemoglobin and heme and are particularly susceptible to these deleterious pathways (PMID 31455889).In patients with sickle cell anemia, increased markers of hemolysis and hemoglobinuria are risk factors for kidney disease and kidney disease progression (PMID 24329963). Voxelotor is a small molecule allosteric modulator that binds and maintains sickle hemoglobin in the oxygenated state, thereby preventing hemoglobin S polymerization and red blood cell sickling. In a phase 3 study, voxelotor improved the degree of hemolysis, as reflected by a rise in hemoglobin concentration and a reduction in indirect bilirubin and reticulocyte percentage (PMID 31199090). The benefits of reducing hemolytic anemia with voxelotor on kidney function are unknown.We investigated whether GBT1118, an analogue of voxelotor with improved pharmacokinetic properties in transgenic sickle mice, would improve biomarkers of kidney damage and kidney function in sickle cell anemia. Transgenic sickle mice (Hb SS; Townes model, Jackson Laboratory) were treated with either GBT1118 (5 male, 5 female) or control (5 male, 5 female) chow from 12 to 24 weeks of age. Urine was collected using metabolic cages for 24 hours at 3 week intervals and blood was collected at baseline, 6 weeks, and 12 weeks of therapy. We compared markers of hemolysis (hemoglobin, reticulocyte percentage), reactive oxygen species (thibarbituric acid reactive substances [TBARS], kidney injury (kidney injury molecule-1 [KIM-1], nephrin), and kidney function (urine albumin and protein, serum blood urea nitrogen [BUN] and creatinine) at the respective time points using ANOVA and adjusting for gender. Mean and standard error values are provided.Consistent with the clinical results observed in the voxelotor phase 3 study, we observed significant improvements in the hemoglobin concentrations and reticulocyte percentages of Hb SS mice treated with GBT1118 versus control (Figure 1A and 1B). The hemoglobin occupancy of GBT1118 after 6 weeks (33 ± 2%) and 12 weeks (28 ± 2%) of therapy were also similar to what was observed in the phase 3 clinical study. An improvement in hemolysis led to reduced hemoglobinuria (6 weeks: treated = 0.07 ± 0.03 vs. control = 0.72 ± 0.2 ng/day, P = 0.004; 12 weeks: treated = 0.04 ± 0.03 vs. control = 1.06 ± 0.32 ng/day, P = 0.006) and less oxidant damage in the kidneys, assessed by urine TBARS concentration, in the treated versus control mice (6 weeks: treated = 31 ± 6 vs. control = 60 ± 10 nmol/day, P = 0.001; 12 weeks: treated = 29 ± 4 vs. control = 71 ± 9 nmol/day, P < 0.001).At 24 weeks of age, markers of glomerular (nephrin: treated = 3.5 ± 0.7 vs. control = 8.5 ± 1.6 ng/day) and tubular injury (KIM-1: treated = 169.6 ± 19.4 vs. control = 348.9 ± 48.2 pg/day) were significantly improved in the treated versus control Hb SS mice (P< 0.001) (Figure 1C). Albuminuria remained stable in the treated Hb SS mice and was relatively close in value to the degree of albuminuria observed in Hb AA mice (Figure 1D). In contrast, albuminuria progressively increased with older age in the control Hb SS mice. A similar pattern was observed for proteinuria (24 week: Hb SS treated = 2.02 ± 0.17 mg/day, Hb SS control = 3.65 ± 0.44 mg/day, Hb AA = 1.65 ± 0.27 mg/day). At 24 weeks of age, the treated Hb SS mice had serum BUN and creatinine values that were similar to what was observed at 12 weeks of age in the Hb SS mice and to the 24-week old Hb AA mice (Figure 1E, 1F). Furthermore, the values for serum BUN and creatinine were significantly lower in the treated versus control Hb SS mice at 24 weeks of age (P ≤ 0.04).In conclusion, we demonstrate that an improvement in hemolysis results in preserved kidney function in transgenic sickle mice. Our findings highlight the clinical importance of hemolytic anemia in the pathophysiology of sickle cell nephropathy. Our results also provide support for developing strategies to mitigate hemolysis in sickle cell anemia in order to provide a targeted approach to improve kidney disease, a devastating complication associated with high morbidity and mortality, in sickle cell anemia. [Display omitted] DisclosuresGordeuk: Modus Therapeutics: Consultancy; Novartis: Research Funding; Incyte: Research Funding; Emmaus: Consultancy, Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; CSL Behring: Consultancy. Saraf: Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding.

Hydroxyurea treatment and neurocognitive functioning in sickle cell disease from school age to young adulthood.

Neurocognitive impairment is common in sickle cell disease (SCD) and is associated with significant functional limitations. In a cross-sectional analysis, we examined the association between hydroxyurea (HU) treatment and neurocognitive functioning from school-age to young adulthood in individuals with SCD. A total of 215 patients with HbSS/HbSβ0 -thalassaemia (71% HU treated) and 149 patients with HbSC/HbSβ+ -thalassaemia (20% HU treated) completed neurocognitive measures at one of four developmental stages: school-age (age 8-9years), early adolescence (age 12-13years), late adolescence (age 16-17years) and young adulthood (ages 19-24years). For participants with multiple assessments, only the most recent evaluation was included. In multivariable analysis adjusted for social vulnerability, HU treatment and sex, older age was associated with a reduction in overall intelligence quotient (IQ) of 0·55 points per year of life [standard error (SE) = 0·18, false discovery rate adjusted P value (PFDR) =0.01] for patients with HbSS/HbSβ0 -thalassaemia. Earlier initiation of HU (n=152) in HbSS/HbSβ0 -thalassaemia was associated with higher scores on neurocognitive measures across most domains, including IQ [estimate (SE) 0·77(0·25)/year, PFDR=0·01], after adjusting for social vulnerability, sex and treatment duration. These results support the early use of HU to limit the detrimental neurocognitive effects of SCD, while highlighting the need for additional measures to further mitigate neurocognitive deterioration.

Effects of Renin-Angiotensin Blockade and APOL1 on Kidney Function in Sickle Cell Disease.

Effects of Renin-Angiotensin Blockade and APOL1 on Kidney Function in Sickle Cell Disease.

The vasculopathic cord between pre-eclampsia and kidney function in sickle cell disease.

The vasculopathic cord between pre-eclampsia and kidney function in sickle cell disease.

Cerebral Hemodynamics and Executive Function in Sickle Cell Anemia.

Individuals with sickle cell anemia experience cognitive deficits, even in the absence of cerebral infarcts or strokes. This study tested the hypothesis that elevated cerebral blood flow and oxygen extraction fraction are associated with lower executive function in individuals with sickle cell anemia. Three-Tesla brain magnetic resonance imaging was performed, including anatomic, gray matter cerebral blood flow, and global oxygen extraction fraction imaging. Executive function was measured using the working memory index from an age-appropriate Wechsler battery and tasks from the National Institutes of Health Toolbox Cognition Battery. Bivariate and multivariate models were examined (significance: P<0.05). Fifty-four participants (age range=6-31 years) with sickle cell anemia were enrolled. Hematocrit was positively related to fluid cognition, cerebral blood flow was inversely related to working memory and inhibitory control, and oxygen extraction fraction was inversely related to processing speed. Associations remained significant in multivariate analyses controlling for age, income, and infarcts. Elevated cerebral blood flow and oxygen extraction fraction, markers of hemodynamic impairment, are associated with deficits in executive function in individuals with sickle cell anemia.

Using machine learning to predict rapid decline of kidney function in sickle cell anemia.

Using machine learning to predict rapid decline of kidney function in sickle cell anemia.

Effects of Hydroxyurea and Renin-Angiotensin Blockade on Kidney Function in Sickle Cell Disease

Kidney disease is a common complication that leads to increased morbidity and early mortality in patients with sickle cell disease (SCD). Vaso-occlusion, hyperfiltration, hypertension, and cell-free hemoglobin/heme-mediated toxicity may contribute to the pathophysiology of kidney disease. Treatments for SCD-related kidney disease have been adopted from therapies used to treat other SCD-related complications (hydroxyurea [HU]) or diabetic nephropathy (angiotensin converting enzyme [ACE]-inhibitors or angiotensin receptor blockers [ARBs]), although their effects on kidney function are not clear. We evaluated the effects of HU and ACE-inhibitors or ARBs on kidney function in a longitudinal cohort of 439 SCD patients enrolled into a prospective registry between 2011 and 2019. Patients were considered for the analysis if they had 6 months of kidney function values pre-therapy and remained on therapy for 6 months or longer. Changes in the estimated glomerular filtration rate (eGFR) and urine albumin concentration were compared prior to and after starting therapy using a mixed effects model. The effects of HU on kidney function were evaluated in 49 SCD patients. The mean age was 38 years (standard deviation [SD] 11 years), 43% were male, and 80% were Hb SS/Sβ0-thalassemia genotype. The eGFR improved from an average decline of -3.3 mL/min/1.73m2 in the 6 months prior to starting HU to an increase of +9.5 mL/min/1.73m2 during HU therapy (P = 0.0002) (Table). The average change in albuminuria also improved from an increase of +1.2 mg/g creatinine pre-HU therapy to a decline of -1.2 mg/g creatinine during HU therapy, although the difference was not statistically significant (P = 0.17). In 47 SCD patients started on ACE-inhibitors or ARBs, the mean age was 45 years (SD 11 years), 43% were male, and 87% were Hb SS/Sβ0-thalassemia genotype. During ACE-inhibitor or ARB therapy, there was no observed difference in the change in eGFR pre- versus during therapy (P = 0.9) (Table). Albuminuria improved from an average change of -1.0 mg/g creatinine pre-therapy to -1.6 mg/g creatinine during therapy (P = 0.009). Because clinical data are limited, current American Society of Hematology guidelines have conditional recommendations with low levels of certainty for the use of HU and ACE-inhibitors or ARBs to treat sickle cell nephropathy. In a longitudinal cohort of SCD patients, we demonstrate that during 6 months of therapy, there may be a benefit of HU in improving eGFR and of ACE-inhibitors or ARBs in reducing albuminuria. Larger and longer follow up studies of HU, ACE-inhibitors and ARBs as well as new targeted therapies to treat sickle cell nephropathy are urgently needed. Figure Disclosures Gordeuk: Novartis: Consultancy; Ironwood: Research Funding; CSL Behring: Consultancy, Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; Imara: Research Funding. Saraf:Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Boards, Speakers Bureau; Novartis, Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pfizer, Global Blood Therapeutics, Novartis: Research Funding.

Fetal Hemoglobin Mediates the Effect of Beta Globin Gene Polymorphisms on Neurocognitive Functioning in Sickle Cell Disease

Background: Fetal hemoglobin (HbF) is the most influential modifier of the clinical and hematologic phenotype of sickle cell disease (SCD) and is highly heritable. Low HbF is independently associated with increased white matter changes on brain imaging and poorer performance on neurocognitive measures (Ruffiuex, Child Neuropsychology, 2013). Our previous work has shown that 11 SNPs in three genes (BCL11A, MYB, and β-globin), contribute over 20% of the variance in HbF (Rampersaud, Kang. et al., 2020, under review). Clinically, these HbF-associated SNPs are associated with disease severity and frequency of pain events. However, the neurocognitive implications of these SNPs have yet to be explored. As part of a prospective longitudinal cohort study, the Sickle Cell Clinical Research and Intervention Program (SCCRIP), we evaluated the relationship between HbF-associated SNPs and neurocognitive functioning in SCD patients. Methods: We included 257 patients with SCD (69% HbSS/HbSβ0-thalassemia). The median age of participants was 13 years (range 4 - 25). We extracted genotypes for the 11 HbF-associated SNPs from whole genome sequencing data and analyzed them based on an additive genetic model. Following informed consent, patients completed a battery of gold-standard neurocognitive measures, supervised by a psychologist, assessing IQ, verbal and perceptual reasoning, working memory, processing speed, sustained attention, and executive functioning skills. HbF was the average value of measurements collected within 3 months of neurocognitive assessment, or the closest value. In univariate analyses, Kruskal-Wallis rank sum test was used to assess the associations of the 11 HbF-associated SNPs with neurocognitive measures. Linear regression was used to examine these associations adjusting for age, sickle genotype, hydroxyurea exposure, socioeconomic status (index of social vulnerability) and 5 principal components to adjust for population stratification. Benjamini and Hochberg false discovery rate (FDR) was used for multiple corrections and FDR adjusted p (pFDR)&amp;lt;0.05 was considered significant for all analyses. Mediation analyses (Imai, Psychological Methods, 2010) were used to evaluate the indirect effects of HbF-associated SNPs on neurocognitive outcomes via HbF. Results: One SNP in the β-globin gene, rs968857, was associated with performance on measures of IQ, verbal reasoning, working memory, and executive functioning by Kruskal-Wallis rank sum test (Figure 1) and by linear regression adjusting for covariates listed above at pFDR &amp;lt;0.05. HbF expression was positively associated with IQ and verbal reasoning scores at pFDR &amp;lt;0.05 using linear regression adjusting for age, sickle genotype, hydroxyurea exposure, and socioeconomic status. HbF mediated the relationship between rs968857 and scores on IQ and verbal reasoning measures at pFDR &amp;lt;0.05 (Figure 2). The direct effect of rs968857 on neurocognitive functioning remained significant following inclusion of HbF at pFDR &amp;lt;0.05, indicating partial mediation. Full linear regression models with rs968857, HbF, and covariates accounted for 10.8%, 14.5%, 6.4%, and 8.3% of the variance in IQ, verbal reasoning, working memory, and executive functioning measures, respectively. Conclusions: This is the first study to demonstrate a relationship between genetic modifiers of SCD and neurocognitive functioning. Beyond findings on neuroimaging and sociodemographic factors, there is little known about risk for neurocognitive deficits in SCD. The present results suggest an influence of SNP rs968857 on cognitive function, which was partially mediated by expression of HbF. rs968857, is one of four SNPs that defines almost all β-globin gene cluster haplotypes and influences HbF levels in SCD. How this SNP effects HbF and neurocognition is unknown and requires further investigation of its mechanism. The highly heritable nature of HbF may allow for future use of precision medicine. SCD patients could be stratified according to risk for neurocognitive deficits to utilize early intervention strategies, informed by genetic polymorphisms. Correlation with neuroimaging will help further elucidate the relationship between genetic modifiers and neurocognitive functioning. Future trials with larger samples are needed to validate our findings and investigate if the observed relationships differ by age or hydroxyurea treatment status. Disclosures Estepp: Daiichi Sankyo, Esperion, Global Blood Therapeutics: Consultancy; Global Blood Therapeutics, Forma Therapeutics, Pfizer, Eli Lilly and Co: Research Funding; ASH, NHLBI: Research Funding. King:Amphivena Therapeutics: Research Funding; Bioline: Consultancy; Celgene: Consultancy; Cell Works: Consultancy; Incyte: Consultancy; Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees; Novimmune: Research Funding; RiverVest: Consultancy; Tioma Therapuetics: Consultancy; WUGEN: Current equity holder in private company. Hankins:Novartis: Research Funding; National Heart, Lung, and Blood Institute: Honoraria, Research Funding; UptoDate: Consultancy; Global Blood Therapeutics: Consultancy, Research Funding; MJH Life Sciences: Consultancy, Patents &amp; Royalties; American Society of Pediatric Hematology/Oncology: Honoraria; LINKS Incorporate Foundation: Research Funding.

Asthma, allergic sensitization and lung function in sickle cell disease

BackgroundPulmonary disease is a frequent acute and chronic manifestation in sickle cell disease (SCD), presenting high morbidity and mortality. ObjectivesTo identify the prevalence and association of asthma, allergic sensitization and altered pulmonary function in patients with SCD (SS and Sβo). MethodsA single-center, cross-sectional study was conducted, in which 70 patients with SCD and 44 controls, aged six to 18 years, responded to the questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC), complemented with an anamnesis regarding the associated clinical outcomes. All patients underwent immediate hypersensitivity skin tests with aeroallergens and a pulmonary function evaluation (spirometry). Regarding the statistical analysis, parametric and non-parametric methods were used, depending on the variables studied. Tests were considered significant when p<0.05. ResultsThere was no significant difference between the patients and controls regarding the prevalence of asthma and allergic sensitization (p>0.05). The number of occurrences of acute chest syndrome per patient per year was significantly higher for asthmatic patients than for non-asthmatic patients (p=0.04). Obstructive pulmonary function occurred in 30.9% of the patients and in 5.4% of the controls, and restrictive pulmonary function occurred in 5.5% of the patients and 5.4% of the controls. Asthma and wheezing in the last 12months had significant associations with obstructive pulmonary function (p=0.014 and p=0.027, respectively). ConclusionsThe occurrence of asthma, allergic sensitization and alteration in lung function in patients with SCD reinforces the importance of routine monitoring of these diagnoses, which allows for early treatment and prevention of the evolution of pulmonary disease in adulthood.

Correlates of Cognitive Function in Sickle Cell Disease: A Meta-Analysis.

To provide a comprehensive quantitative review of biological, environmental, and behavioral correlates across domains of cognitive function in sickle cell disease (SCD). Forty-seven studies were identified in PubMed, MedLine, and PsycINFO involving 2573 participants with SCD. Meta-analytic findings across all identified samples indicate that hemoglobin and hematocrit were positively correlated with Full Scale IQ [FSIQ; r = .15, 95% confidence interval (CI) = .10 to .21], language and verbal reasoning (r = .18, 95% CI = .11 to .24), and executive function (r = .10, 95% CI = .01 to .19) with small effects and significant heterogeneity. Transcranial Doppler velocity was negatively associated with visual spatial and perceptual reasoning (r = -.18, 95% CI = -.31 to -.05). Socioeconomic status was positively associated with FSIQ (r = .23, 95% CI = .17 to .28), language and verbal reasoning (r = .28, 95% CI = .09 to .45), visual spatial and perceptual reasoning (r = .26, 95% CI = .09 to .41), and executive function (r = .18, 95% CI = .07 to .28) with small to medium effects. Finally, total behavioral problems were negatively associated with FSIQ (r = -.12, 95% CI = -.21 to -.02) such that participants with lower FSIQ exhibited greater behavioral and emotional problems. Findings provide evidence for biological, environmental, and psychosocial corelates across multiple domains of cognitive function in SCD. More research on more specific cognitive domains and psychosocial correlates is needed in addition to assessments of interactional models among risk factors.

Non-invasive urinary biomarkers of renal function in sickle cell disease: an overview.

Sickle cell disease (SCD) is a hereditary condition characterized by homozygosis of the hemoglobin S (HbS) gene. Marked morbimortality is observed due to chronic hemolysis, endothelial injury, and episodes of vaso-occlusion, which leads to multi-organ damage. Renal impairment is common and may have different presentations, such as deficiency in urinary acidification or concentration, glomerulopathies, proteinuria, and hematuria, frequently resulting in end-stage renal disease (ESRD). Novel biomarkers of renal function, such as kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) and monocyte chemoattractant protein 1 (MCP-1) are being studied in order to enable early diagnosis of kidney damage in SCD.