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

BACKGROUND AND OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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 . CONCLUSION: 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.

Red-blood-cell alloimmunization and prophylactic antigen matching for transfusion in patients with warm autoantibodies.

BACKGROUND: Warm autoantibodies (WAA) are antibodies that react with an antigen on a patient's own red-blood-cells and can complicate compatibility testing whether or not they cause clinical haemolysis. The goal of this study was to understand the overall prevalence of WAA, the risk of RBC alloimmunization and determine whether RBC selection practices have an impact on alloimmunization. MATERIALS AND METHODS: Records of patients (>1 year of age) with an indirect antibody detection test (IAT) and serologic evidence of WAA over a 10-year-period were included. Eight centres from 5 countries collectively reviewed 1 122 245 patients who had an IAT. RESULTS: Of patients having IAT, 1214 had WAA (0·17%). Transfusion information for 1002 of the patients was available; 631 were transfused after identification of the WAA (63%); of the transfused patients, 390 received prophylactic antigen-matched (PAM) RBCs and 241 did not. Of the 372 patients with WAA who were transfused and had serologic testing 30+ days following transfusion (30-2765 days), 56 developed new RBC alloimmunization (15·1%). Patients who were transfused using a PAM strategy were not protected from new RBC alloimmunization [14·6% (31 of 212 patients) having PAM transfusion approach compared with those not receiving PAM approach (15·6%, 25 of 160 patients, P = 0·8837)]. CONCLUSIONS: The prevalence of WAA in patients having an IAT is low (<1%). A significant portion of patients with WAA form new RBC alloimmunization (15·1%); however, the use of PAM approach for RBC selection was not found to be protective against new alloimmunization.

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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Alloimmunization in autoimmune hemolytic anemia patient: The differential adsorption approach.

Patients of ß-thalassemia major are dependent on regular blood transfusions for their entire lifetime. Development of antibodies against red blood cell (RBC) antigen which may be alloantibody or autoantibody, several times as a result of frequent red cell component transfusions, further complicates the subsequent transfusion therapy. Among the autoantibodies, warm-reactive autoantibodies are commoner and interfere in the pretransfusion testing. These RBC autoantibodies present in patient's serum potentially react with all the cells of antibody identification panel giving "pan-reactive" picture and making alloantibody identification complex. In this report, we present our approach in a thalassemia patient who presented with warm-type autoimmune hemolytic anemia, low hemoglobin of 5.8 g/dl, and three significant alloantibodies (anti-D, anti-S, and anti-Jkb) which were masked by pan-reactive warm autoantibody(s). Differential adsorption was used to unmask underlying alloantibodies. We suggest that differential adsorption procedure is an effective and efficient method for autoantibody adsorption, detection, and identification of masked alloantibody(s), especially in patients with low hemoglobin and history of recent blood transfusion.

Drug-induced autoimmune hemolytic anemia in a 78-year-old African-American man with chronic lymphocytic leukemia.

PATIENT: 78-year-old African-American man. PAST MEDICAL HISTORY: Chronic lymphocytic leukemia first diagnosed in 2003, with a subsequent relapse in 2006 and another in 2010. HISTORY OF PRESENT ILLNESS: In late 2011, the patient was admitted to the hospital for cholelithiasis, at which time his treating physician incidentally discovered severe anemia. The anemia worsened as time went on, and the patient became transfusion dependent. Hypogammaglobulinemia secondary to chronic lymphocytic leukemia (CLL) required that the patient receive intravenous immunoglobulin. Despite transfusion therapy, the anemia failed to lessen; laboratory results eventually led to the diagnosis of a drug-induced warm autoantibody that triggered hemolytic anemia. MEDICATIONS: The patient had taken rituximab in 2003; rituximab, cyclophosphamide, hydroxydaunorubicin, oncovin, and prednisone (R-CHOP) in 2006; fludarabine, cyclophosphamide, and rituximab (FCR) in 2010; and intravenous Immunoglobulin (IVIG) and prednisone in 2011.