Warm Autoantibodies Research Articles

Mixed autoimmune hemolytic anemia during recovery from Immune Thrombocytopenia (ITP): A Case Report

Mixed autoimmune hemolytic anemia (AIHA) is characterized by hemolysis with the coexistence of warm and cold autoantibodies. It is a relatively rare condition, accounting for 6.5-8.3% of AIHA cases. It is diagnosed by identifying IgG and C3d with cold agglutinins on monospecific direct antiglobulin testing. We present a unique case of a 69-year-old female who developed mixed hemolytic anemia while she was being treated for chronic idiopathic thrombocytopenic purpura (ITP).

Warm reactive autoantibodies detected by solid phase technology: Patient characteristics, laboratory features, and clinical significance.

This study focused on the serology, clinical characteristics, and hemolytic potential of warm reactive autoantibodies detected by solid phase red cell adherence. Ninety-seven patients with warm autoantibodies were evaluated. Serologic characteristics included the strength of solid phase reactivity, the results of tube-based ancillary testing, direct antiglobulin test and eluate results, and an assessment for contemporaneous alloantibodies. Clinical characteristics of the patients included age, sex, and primary diagnosis. Each patient was also assessed for evidence of hemolysis. Most of the 97 study patients were female (63.9%), and the average age was 66 years. Hematologic disorders were the most common diagnosis. A majority (70.1%) of the warm autoantibodies had 3 to 4+ reaction strengths, and approximately 90% had negative testing with at least 1 test tube method. There was an even distribution of direct antiglobulin test reaction strengths, with 74% reactive with anti-immunoglobulin G only. Alloantibodies were identified in 20% of patients. Evidence of hemolysis was identified in only 13 patients (13.4%). Warm reactive autoantibodies are more likely to be hemolytic, have strongly reactive indirect and direct antiglobulin tests, remain reactive in tube-based ancillary testing methods, and are seen primarily in patients with hematologic disorders.

Post-transfusion biotin-labeled red blood cell survival studies in pediatric sickle cell disease with antibodies of uncertain significance.

Red blood cell (RBC) antibodies are common in multiply transfused patients with sickle cell disease (SCD). Unlike RBC alloantibodies, the potential of autoantibodies to cause post-transfusion hemolysis may be uncertain. Biotin-labeling provides a direct measurement of red cell survival (RCS) over time, thus can be used to assess the clinical significance of RBC antibodies. Antibodies to biotinylated RBC (B-RBC) occasionally are detected after exposure, which may impact B-RBC survival in subsequent RCS studies. Pediatric patients with SCD receiving monthly chronic transfusions underwent RCS studies, receiving aliquots of allogeneic RBC labeled at distinct densities of biotin (2-18 μg/mL). B-RBC survival was followed for 4 months post-transfusion, and B-RBC antibody screening for 6 months. Patients with warm autoantibodies (WAA) or B-RBC antibodies are reported here. RBC antibodies were detected during RCS in four patients: one with WAA, one with WAA followed by B-RBC-specific antibodies, and two with transient B-RBC antibodies within the first 5 weeks of exposure. B-RBC half-lives (T50) ranged 37.6-61.7 days (mean 47.8 days). There was no evidence of increased hemolysis or accelerated B-RBC clearance in the presence of WAA or B-RBC antibodies. Biotinylation of allogenic RBC can be used to assess the possible effects of RBC antibodies on transfusion survival in individual cases, particularly when it is uncertain if the detected antibodies may result in hemolysis. In the cases presented here, neither WAA nor B-RBC antibodies were associated with significant shortening of B-RBC survival in individuals with SCD.

Clinical profile and serological correlation with haemolysis in DAT-positive autoimmune haemolytic anaemia patients in Bangladesh

Discerning the type of autoimmune haemolytic anaemia (AIHA) is crucial for transfusion support and initiation of treatment. This study aimed to establish the clinical profile and serological character of red cell autoantibodies and to investigate the relationship with haemolysis in AIHA patients who were direct antiglobulin test (DAT)-positive. A total of 59 DAT-positive AIHA patients were included in this study. Clinical, laboratory and serological findings were evaluated to find the gradation of haemolysis and to investigate its correlation with age, sex, type of autoantibody and level of autoantibody. Study findings revealed that most patients (89.8%) had haemolysis, wherein moderate haemolysis (67.8%) was predominant. Weakness, palpitations, fever, pallor, tachycardia and splenomegaly were common among patients with severe and moderate haemolysis. The majority (66.1%) had an associated disorder. Warm autoantibody was the most common, followed by cold and mixed cases. The severity of haemolysis correlated strongly with the strength of the DAT reaction (Cramer V 0.636, p<0.001). These findings may be useful to clinicians while determining a treatment plan. The direct relationship between severity of haemolysis and strength of DAT needs further exploration in a large population to establish whether it can be used as a tool to formulate a treatment plan when assessing AIHA patients in low resourced countries.

The impact of an antibody investigation algorithm emphasizing specificity on reducing potential false-positive warm autoantibody detection at a Canadian tertiary care centre.

To reduce potential false-positive warm autoantibody (WAA) by solid-phase red cell adherence assay (SPRCA), our centre implemented a new antibody investigation algorithm (AIA) by classifying cases with panreactive SPRCA but negative saline-indirect antiglobulin test as 'antibody of undetermined significance' (AUS) after excluding clinically significant antibodies. We assessed the effects of the new AIA and subsequent alloantibody formation in patients with AUS. Samples from patients with positive SPRCA screens between 1 September 2017 and 31 August 2021 were selected for the study. Frequencies of antibodies classified by the old and new AIAs were compared using Fisher's exact test. Patient demographics, transfusion history and antibody formation in cases of AUS were collected. A significant reduction in potential WAA frequencies from 127/1167 (11%) to 53/854 (6%) was observed (p < 0.001) when compared between the old and new AIAs among 2021 positive SPRCA antibody screens. While no patients with AUS later transitioned to potential WAA using the new AIA, four patients developed alloantibodies, including anti-E, anti-C, both anti-C and anti-E, and anti-Wra . A significant reduction in the frequencies of potential false-positive WAA detection at our centre was observed after implementing the new AIA, leading to less resource and phenotypically matched red blood cell (RBC) use. Some patients still developed subsequent RBC alloimmunization, so clinically relevant alloantibodies should be carefully excluded before determining AUS, taking forming or evanescent antibodies into consideration.

Rare case of refractory mixed autoimmune hemolytic anemia in a 6-year-old child: a case report

BackgroundMixed autoimmune hemolytic anemia (AIHA) shows combined clinical and laboratory characteristics of warm and cold AIHA. It is relatively uncommon in children. Consequently, knowledge about mixed AIHA prevalence, clinical presentation, treatment options, and prognosis in children is limited to very few case reports.Case presentationWe describe a six-year-old Asian girl presenting with profound anemia, blood group typing discrepancy and crossmatch incompatibility, post upper respiratory tract infection. Detection of red cell warm and cold reactive autoantibodies, led to the diagnosis of mixed AIHA. Autoantibodies with laboratory evidence of hemolysis persisted despite high dose steroid therapy. Due to the inability to wean further, the patient was subsequently commenced on mycophenolate mofetil to which she seems to be responding.ConclusionsMixed AIHA may be notoriously difficult to diagnose and treat. Detailed clinical and laboratory work-up is essential to establish the diagnosis. To the best of our knowledge, this is the first case report of mixed AIHA following upper respiratory tract infection. Awareness of this occurrence is important, as similar to warm AIHA, mixed AIHA should be treated immediately by early initiation of steroid therapy. In addition, prompt supportive care as well as long-term clinical follow-up are required to improve outcomes of these cases.

Eleven years of alloimmunization in 6496 patients with sickle cell disease in France who received transfusion

AbstractRed blood cell (RBC) transfusion is a major therapy for sickle cell disease (SCD). Patients are at risk of forming antibodies to RBC antigens, which can result in the impossibility to find compatible units and can cause hemolytic transfusion reactions. This retrospective study investigates the evolution of RBC consumption and the frequencies, specificities, and chronology of the appearance of antibodies in a population of patients consistently receiving RH (C, D, E, c, e) and K–matched RBC units (RBCus) from a predominantly European donor population. Over the 11-year period in the Paris area, 6496 patients received transfusion at least once for a total of 239 944 units. Antibodies were made by 1742 patients. The first antibodies of a patient were predictive of subsequent immunization. By the 17th RBCu transfused (by the 20th, excluding warm autoantibodies), 75% of the patients who would make antibodies had made their first. By the 16th, 90% who would make antibodies to a high frequency antigen had made their first antibody to these antigens. Females made their first antibodies slightly earlier than males. Patients who received multiple transfusions (>50 units) had a higher immunization prevalence than those who rarely received transfusion (<12 units) but fewer clinically significant antibodies. Patients with SCD and prophylactic RH-K matching not immunized by the 20th RBCu are likely to have a low alloimmunization risk (to antigens other than RH-K), that is, be low responders, especially relative to the most clinically significant antibodies. This number of 20 units is a point before which close monitoring of patients is most important but remains open to future adjustment.

Evidence that donors with variant RH genotypes are associated with unexpected Rh antibodies.

We previously reported unexpected Rh antibodies in the plasma of patients with sickle cell disease (SCD) that demonstrated common Rh specificities in the absence of transfusion of RBCs positive for that antigen. We hypothesize that these antibodies might result from transfusion of antigen-negative donor units with variant RH genotypes. Plasma testing by tube and IgG gel, extended RBC phenotyping, and HEA and RH genotyping were by standard methods. A 6-year-old female with SCD, phenotype D + C-c + E-e + K- undergoing exchange transfusion with CEK- and Fy(a-) units, presented with anti-C in the plasma, a + DAT and warm autoantibody (WAA) in the eluate. Her RH genotype was unremarkable: RHD*D/DAU0 and RHCE*ce/ce(48C). Units (n = 10) transfused over the prior 6 months were confirmed CEK- by serology and DNA testing. Most (n = 7) were Rh-negative. A unit with variant RH, RHD*DIIIa/weak partial 4.0, RHCE*ceVS.03/ceVS.02, was transfused 5 weeks prior. Anti-C and + DAT continued to demonstrate for 25 weeks. Total hemoglobin and % Hgb S did not deviate from her established baseline. We show direct association of plasma anti-C with transfusion of a C-negative unit with variant RH encoding partial D and uncommon V/VS+ hrB - phenotype. The antibody was transient, without evidence of compromised survival of transfused RBCs. The +DAT and WAA complicated workups and selection of units, and it is uncertain whether donors of the same genotype should be avoided. Minority donors are important for CEK-matching to avoid depleting Rh-negative supplies. Consideration of patient and donor RH genotypes may avoid unexpected antibodies and improve allocation of rare donations.

Forward and reverse typing discrepancy and crossmatch incompatibility of ABO blood groups: cause analysis and treatment

ABSTRACTObjectiveAnalyze the reasons for the mismatch between forward and reverse typing of ABO blood types and the mismatch between cross matching.MethodsWhen the forward and reverse typing do not match, use physiological saline method, polyamine method, anti human globulin method, and anti screening positive samples are used for antibody identification.ResultsThe factors contributing to discrepancies in blood typing between forward and reverse typing include weakened serum typing, condensation, monoclonal immunoglobulin influence, bone marrow transplantation, and blood type subtypes. The causes of cross matching incompatibility include homologous antibody, warm Autoantibody, cold Autoantibody and daretozumab.ConclusionRegular red blood cell homologous antibody screening should be conducted based on disease type, blood transfusion history, and medication history. Antigen matched red blood cells should be selected for cross matching, and different experimental methods should be used for testing to ensure the safety of clinical blood transfusion.

Immunohematological evaluation of red cell alloimmunization and statistical assessment of various adsorption techniques in warm autoimmune hemolytic anemia

Adsorption techniques are widely applied to detect underlying masked alloantibodies in warm autoimmune hemolytic anemia (WAIHA). We established various adsorption techniques with an aim to detect alloimmunization in WAIHA This study conducted over a period of nine years included 298 patients of WAIHA. Complete immunohematological evaluation was performed on these 298 samples following departmental protocols. Clinical and laboratory details of patients were obtained from patient files. Various adsorption methods were performed and statistically evaluated in the study. Out of 479 cases of autoimmune hemolytic anemia, WAIHA comprised of 62.2 % (N = 298). A total of 139 (46.6 %) serum samples revealed autoantibodies. Adsorption study was performed in 101 (72.7 %) indicated samples and 24 (23.8 %) of these showed 26 alloantibodies. Among the patients subjected to adsorption study hemolytic marker were significantly deranged in the alloimmunization group (p < 0.01). Polyethylene glycol (PEG) adsorption was the quickest (52.2–54.6 min) of all adsorption techniques with minimum (1.3–1.5) numbers of adsorptions needing for complete removal of serum antibodies. The LISS-papain (LP) technique was found to be more sensitive and specific compared to the other two techniques. The agreement between PEG adsorption and LP adsorption was found to be ‘perfect’ (96.4 %) with a Cohen’s kappa (k) value of 0.9. We conclude that identification of alloantibody specificities underlying a warm autoantibody is critical for a safe and effective transfusion. All WAIHA patients with history of blood transfusion, pregnancy or both should be subjected to adsorption study. Selection of a suitable adsorption technique depends on multiple important factors.

The Incidence of Evanescent Antibodies to Red Blood Cell Antigens in a Tertiary Care Hospital in Northern India

Background and Objectives: The anti-A and anti-B are naturally occurring antibodies in the human body but alloantibodies may be formed in individuals who lacks that corresponding red cell antigen after any sensitising event like blood transfusion or pregnancy. The aim of this study was to find the incidence of evanescenct RBC alloantibodies that may not be detectable at the time of pre-transfusion screening. Methods: This was a retrospective observational study from January 2017 to May 2019 in a tertiary care centre from North India. The data on antibody screening and identification retrieved from the departmental records. The patients were screened for red blood cell antibody and those with a positive screening test were further investigated for antibody identification. Antibody screening was performed by solid phase method using Immucor Capture-R Ready Screen (4 cell). Confirmed positive samples were investigated with advance methods of Antibody ID using Reagent panel Red Blood Cells Capture-R Ready ID (16 Cell) in Automated Analyzer Iris or Neo (Immucor Inc. Nocross, GA, USA). As and when required other advance techniques of adsorption and elution, etc were also performed too. Results: The total number of patient screened during this period were 8071. Amongst them 312 were positive for antibody screening (3.8%), of those 216 (62.9%) cases had alloantibodies and 96 (30.7%) cases had autoantibodies. Among the 216 cases of alloantibody, 147 (68.1%) cases had single alloantibody and 69 (31.9%) cases had multiple alloantibodies. Amongst the patients having single alloantibody, the prevalence was highest for Anti-D 54 (36.7%), followed by Anti-E 27 (18.3%), Anti-C 8 (5.4%), Anti-c 7 (4.7%), Anti-K 9 (6.1%), Anti-Fyb 11 (7.4%), Anti-M 18 (12.2%), Anti-N 4 (2.7%), Anti-Fyb 3 (2%), Anti-Lea 3 (2%), Anti-Cw 2 (1.3%) and Anti-Mia 1 (0.6%). Of the 96 patients with autoantibody 72 had warm autoantibody, 10 had cold autoantibody and there were 8 cases of mixed warm and cold autoantibodies. There were 6 patients with warm autoantibody with underlying alloantibody. Conclusion: In conclusion, the high prevalence of Anti-Rh (Anti-D, E), Anti-M, Anti-Fyb antibodies in patient requiring transfusion reiterates the importance of stringent antibody screening and identification as an essential step in preventing delayed hemolytic transfusion reaction.

Implementation of a molecular genotyping protocol for patients with warm autoantibodies.

Warm autoantibodies (WAAs) cause delays and additional expenses while determining suitable products when using a traditional protocol (TP). In 2013, Carter BloodCare Immunohematology Reference Laboratory (IRL) introduced a molecular protocol (MP) for patients with WAAs. Retrospective review of records for samples referred to the IRL from November 2004 to September 2020, was performed. Referrals, alloantibody(ies), gender, and age were recorded. Additionally, the count of common clinically significant antigens needed for phenotypically matched red blood cells (RBCs) were recorded for patients in MP. To further analyze charges and time spent testing patients with WAAs, 300 patients were selected. Analysis of average charges to the referring hospital and time spent testing in the IRL determined savings at two or more referrals. Overall, 219 of 300 (73%) of patients in the study met or exceeded the number of referrals. Further analysis shows that while the population of patients with WAA (n = 300) shared similar demographics, there was a statistically significant difference between the average time testing patients in TP (M = 264.18, SD = 15.06) and MP (M = 156.00, SD = 90.37), t(157) = 14.46, p < .001, 95% confidence interval [CI] (93.41-122.97). Additionally, the assumption that each patient received two RBCs per referral provided no statistically significant difference between average charges to the hospitals of patients in TP (M = 1222.58, SD = 165.69) and MP (M = 1269.78, SD = 433.52), t(192) = -1.25, p = .214, 95% CI (-121.95-27.54). The MP has been effective in saving time spent testing patients with WAAs, which benefits referring hospitals, patients, and IRLs. Charges for prophylactic phenotypically matched blood were negligible and a MP would alleviate some of the current laboratory difficulties while providing safe products to patients.

Mixed Autoimmune Hemolytic Anemia in a 2-Year-Old Girl

Immune hemolytic anemia is diagnosed when it exhibits the clinical symptoms and laboratory findings of hemolytic anemia, such as pallor, jaundice, anemia, high indirect bilirubin, increased reticulocyte count, and a positive direct antiglobulin test. Depending on the type of antigenic stimulation, this condition can be divided into three distinct subtypes: (1) autoimmune hemolytic anemia (AIHA), (2) alloimmune hemolysis, and (3) drug-induced hemolysis. In addition, the thermal amplitude of autoantibodies is used to categorize AIHA as either a warm (most common), cold, or mixed (rare) subtype. Mixed autoimmune hemolytic anemia is diagnosed when both warm and cold autoantibodies are present. Here, we report a case of a mixed AIHA in a 2-year-old girl who responded well to corticosteroids. Due to the rarity of the condition and the lack of rigorous diagnostic criteria, it is crucial to report this case.

Autoantibodies mimicking alloantibodies: A case series unveiling the dilemmas of transfusion.

Autoimmune hemolytic anemia is characterized by increased red cell destruction and/or decreased red cell survival due to autoantibodies directed against self-antigens on red cells. Since autoantibodies react with self and nonself red blood cells (RBCs), they tend to mask the underlying clinically significant alloantibodies and many a times mimic a specific pattern like alloantibodies. We discuss three immune hematological cases of warm autoantibodies. Antibody screening was performed by solid-phase red cell adherence (SPRCA) technique on a fully automated platform NEO Iris (Immucor Inc., USA). In case of a positive antibody screen, antibody identification was performed using SPRCA, NEO Iris (Immucor Inc., USA). Alloadsorption for adsorbing the autoantibodies was done using in-house prepared allogenic packed RBCs - R1R1, R2R2, and rr. All cases had warm autoantibody with a broad specificity against self-Rh antigens. Anti "C" and Anti "e" antibodies were identified in case 1 and autoanti "e" antibody in cases 2 and 3. Case 3 had underlying alloanti "E" along with autoanti "e" which posed a transfusion challenge. Our case series highlights the importance of detecting the nature of the antibody whether it is alloantibody or autoantibody with antigen specificity. This would help in selecting appropriate antigen negative blood units for transfusion purpose.

An Adjusted Process to Improve Efficiency and Efficacy of Adsorption Procedures to Resolve Warm Autoantibody Cases.

The presence of warm autoantibodies in patient plasma typically causes extended delays in patient care due to panreactive antibody identification tests. Adsorption is the primary method for resolution. A modified adsorption procedure was devised with the intent to minimize delays, and the aim of the study was to evaluate its efficacy. To evaluate the in-house developed (experimental) adsorption method, specimens were tested in parallel with the standard adsorption method described in the AABB Technical Manual, 20th edition. Specimens selected demonstrated panreactivity at the submitting facility and contained adequate volume for parallel adsorption studies. Ninety specimens were tested with both methods. Ninety specimens achieved complete adsorption with the experimental method and 88 specimens achieved complete adsorption with the standard method. Two underlying alloantibodies, which have been reported to cause hemolytic transfusion reactions and potential renal graft rejection, were detected using the experimental method that the standard method failed to detect. The experimental method demonstrated a significant reduction in rounds of adsorption required to resolve warm autoantibody reactivity, enhanced antibody detection ability with adsorbed plasma, and more cost-effective outcomes compared to the standard method. A follow-up study is planned to assess whether the incubation time can be decreased with the experimental method to further improve the efficiency of the method without sacrificing efficacy.

Development and exacerbation of autoimmune hemolytic anemia following COVID-19 vaccination: A systematic review.

Autoimmune hemolytic anemia (AIHA) is caused by the production of autoantibodies against RBCs. COVID-19 vaccines can reduce the risk of severe disease, however, various adverse effects such as AIHA were observed following vaccination. This review aimed to assess the relationship of AIHA and COVID-19 vaccination using the PRISMA guidelines. Among 18 cases included in this review, new post-vaccination AIHA development was reported in 11 patients (7 women and 4 men) with a median age of 67.0 years. In 7 of 11 and 3 of 11 cases, the onset of symptoms occurred after first and second vaccine dose with median times of 7 and 14 days, respectively. In 1 of 11 cases, the AIHA occurred on Day 17 after booster vaccination. Ten of 11 and 1 of 11 AIHA patients received mRNA- and vector-based vaccine, respectively. After vaccination, 9 of 11, 1 of 11, and 1 of 11 AIHA patients developed warm IgG, cold IgM, and mixed autoantibodies against RBCs, respectively. Significant AIHA exacerbation was reported in seven patients (four women and three men) with a median age of 73.0 years. In 4 of 7 and 2 of 7 exacerbated AIHA cases, the onset of symptoms occurred after first and second vaccine dose with median times of 7 and 3 days, respectively. In 1 of 7 exacerbated AIHA cases, the onset of symptoms was observed on Day 2 after booster vaccination. All exacerbated AIHA cases received mRNA-based vaccines; 3 of 7 and 4 of 7 exacerbated AIHA cases developed IgG and IgM against RBCs, respectively. This review provides a comprehensive explanation regarding the AIHA development and exacerbation after COVID-19 vaccination.

Warm autoimmune hemolytic anemia with anti-e specificity: A case report

Warm autoimmune hemolytic anemia is a rare condition characterized by warm autoantibody destruction of red blood cells. Antibody specificity cannot be determined in most cases and an apparent autoantibody specificity to a specific antigen is rarely seen. Here we present a case of a 43-year-old female patient presenting with acute small bowel obstruction and requiring an exploratory laparotomy. However, laboratory investigations showed evidence of intravascular hemolysis with normocytic normochromic anemia, reticulocytosis, elevated bilirubin and lactate dehydrogenase levels, and low haptoglobin level. Two units of packed red blood cells were requested. Blood bank investigations including antibody screening, antibody identification panel, direct coombs testing with polyspecific and monospecific anti-human globulin, extended rhesus phenotype, and confirmatory elution testing revealed an IgG autoantibody with anti-e specificity. No compatible units with Rh (e) - positive units were found. However, Rh (e) - negative units’ transfusion was associated with a risk of alloimmunization and a decision of two least incompatible units was taken. So, an anti-e IgG autoantibody was identified which is a rare and challenging clinical condition in terms of diagnosis and transfusion.

Hyperhemolysis in the Setting of Mixed-Autoimmune Hemolytic Anemia: A Rare Complication of COVID-19

SARS-CoV-2 is a novel human pathogen known for its predilection for the respiratory system. Herein, we present a unique case in which a patient developed hyperhemolysis in the setting of mixed autoimmune hemolytic anemia secondary to SARS-CoV-2. A 33 years-old male with a past medical history of resolved immune thrombocytopenic purpura (ITP) presented to the hospital with symptoms of jaundice after being infected with SARS-CoV-2. On admission, his Hgb was 12.5g/dL. Lab results showed indirect bilirubin of 13mg/ dL, LDH at 759 U/L, Haptoglobin &lt;10 and the percent reticulocyte count was 2.33%. A DAT was also positive for C3, IgG, anti-E, in addition to both warm and cold autoantibodies. PCR was positive for COVID-19. Within two days of admission, his Hgb dropped to 5.9g/dL. A total of seven units of pRBC was required to achieve an Hgb of 6g/dL in 48 hours. Patients with preexisting hematological abnormalities have a propensity to develop AIHA in the setting of the virus. The majority of the cases described in the literature were associated with warm autoimmune hemolytic anemia. Our patient tested positive for both warm and cold antibodies, which may partially explain the mechanism behind hyperhemolysis in our patient.

Epidemiology of Hospitalizations Due to Autoimmune Hemolytic Anemia in the United States

Introduction:Autoimmune hemolytic anemia (AIHA) is an acquired immune disorder resulting in the production of cold and warm autoantibodies directed against red blood cell antigens; characterized by shortened red blood cell survival and a positive Coombs test. Types include primary disease (idiopathic) or secondary to other autoimmune disorders, malignancies, or infections. Treatment involves immunosuppression with corticosteroids and other agents, Transfusion. There is not much recent data available on epidemiology of AIHA. We aim to estimate epidemiological trends and outcomes of AIHA as well as factors associated with poor outcomes by using the largest available national database from the United States.Methods:We derived a study cohort from the National Inpatient Sample (NIS) for the years 2007-2018 for hospitalizations due to AIHA by using International Classification of Diseases (9th/10th Editions) Clinical Modification diagnosis codes ICD-9-CM/ICD-10-CM). Other diagnosis and comorbidities were also identified by ICD-9/10-CM codes and Elixhauser comorbidity software. Our primary outcome was discharge disposition following AIHA hospitalization. We utilized multivariable survey logistic regression models to analyze and identify predictors of poor outcomes.Results:Between 2007-2018, a total of 52,814 hospitalizations occurred due to primary diagnosis of AIHA. Burden of hospitalizations remained stable from 4,254 (8.1%) in 2007 to 4,405 (8.3%) in 2018. AIHA patients in the study cohort were mostly above 65 years of age (48.6%) followed by 35-65 years of age (33.7%), females (58.3%) and Caucasians (69.1%). Overall in-hospital mortality of AIHA hospitalizations was 3.1%, and discharge to facility was 11.86%. Median length of stay for AIHA hospitalization was 4-days (interquartile range: 2-days to 6-days). Furthermore, in multivariable logistic regression analysis, increasing age (OR 1.2; 95%CI 1.1-1.3; p<0.001), male gender (OR 1.5; 95%CI 1.2-1.3; p:0.0024), vascular events (OR 1.5 ; 95%CI 1.1-2.0; p:0.0156), teaching hospitals (OR 3.1; 95%CI 1.5-6.5; p:0.002), plasmapheresis (OR 5.5; 95%CI 2.8-10.8; p:0.001) and intravenous immunoglobulins (OR 1.9; 95%CI 1.3-3.0; p:0.001) were associated with higher in-hospital mortality.Conclusion:Our study describes the epidemiology of hospitalizations due to AIHA in the United States from a nationally representative database. We observed that hospitalization burden due to AIHA have remained stable from 2007 to 2018. We also identified factors associated with higher in-hospital mortality and some of which are modifiable. Further studies are required to establish the causal association of these factors to poor outcomes and develop better risk stratification strategies to improve overall outcomes of AIHA. DisclosuresNo relevant conflicts of interest to declare.

Two Individuals with Rare Blocked Antigen Phenomenon and Coinciding Warm Autoantibody Mimicking Alloanti-Jk3 Resolved with JK Analysis

Abstract Introduction/Objective Kidd antigens can bind complement (C3) as well as Kidd specific warm autoantibodies (WAAb). An 838G&amp;gt;A single nucleotide variant (SNV) defines JK*01 and JK*02 which codes the antithetical Jka and Jk b, respectively. Both alleles translate the high prevalence (&amp;gt;99%) Jk3 (JK3). The 130G&amp;gt;A is associated with weak Jka and weak Jkb expression. In vivo binding of non-agglutinating globulins can cause false-negative phenotypes by means of the blocked antigen phenomenon (BAP). Methods/Case Report Transfusions were requested for a 74-year-old Caucasian (CA) female with Evan’s Syndrome, and an 85-year-old African American (AA) female with metastatic uterine cancer. Both had a history of nonspecific WAAb. Direct antiglobulin testing (DAT) detected moderate in vivo sensitization of IgG and C3. They phenotyped Jk(a- b-) with untreated and EDTA glycine-acid (EGA) treated IgG DAT-negative cells. Their serum contained anti-Jk3 reactivity, while a panreactive WAAb in the eluate reacted with Jk3- donor and EGA treated DAT-negative autologous cells. Weak anti-Jka and anti-Jkb reactivity remained in the alloadsorbed serum of the antithetical adsorbing cells. Genetic testing of the CA revealed JK*01W.01(130A)/02 alleles, while cDNA confirmed the alleles would be transcribed into mRNA. Sequencing of the AA detected 130G/A, and 838G/A as well as other silent mutations predicting either a Jk(a+wb+) or Jk(a+b+w) phenotype. The CA received one compatible JK:-3 transfusion, and both individuals benefited from multiple least incompatible transfusions of Jk a+ and/or Jk b+ donors with expected hemoglobin increases (1 g/dL per transfusion). The CA serologically phenotyped Jk(a-b+) 132 days later following prolonged immunosuppressive therapy while a normocytic normochromic anemia and the WAAb persisted. No follow up evaluations of the AA are available. Results (if a Case Study enter NA) NA Conclusion Unexpected BAP can confound immunohematology testing and lead WAAbs mimicking alloanti-Jk3 to be mischaracterized as allogeneic. By predicting phenotypes, genetic analysis can aid serological techniques in antibody characterization and help circumvent complications searching for rare JK:-3 donors.