Positive Indirect Antiglobulin Test in Adult Patients With Primary Warm Autoimmune Hemolytic Anemia: Clinical Significance and Prognostic Effect on Response to Corticosteroids.

Abstract

Background: Primary warm autoimmune hemolytic anemia (PWAIHA) is a subtype of autoimmune hemolytic anemia (AIHA) characterized by premature destruction of red blood cells (RBCs) due to autoantibodies, typically immunoglobulin G (IgG), the cornerstone of which is a positive direct antiglobulin test. The indirect antiglobulin test (IAT) is used as a screening test to detect common and clinically significant RBC alloantibodies in patient serum.

Objective: This study aimed to analyze the prevalence, clinical characteristics, and impact of positive IAT in adult patients with PWAIHA at the time of diagnosis, as well as the response to corticosteroids as the first-line treatment.

Methods: This single-center retrospective case-control study was conducted between September 2002 and May 2024 at King Abdullah University Hospital. We analyzed data from 80 adult patients diagnosed with PWAIHA, aged a minimum of 16 years. After recording baseline investigations, including IAT and antinuclear antibody (ANA), all patients were treated with corticosteroids as first-line treatment. The response rate and prevalence of ANA were compared between the IAT-positive and -negative PWAIHA groups.

Results: Baseline IAT positivity was found in 65% of our patients. Both groups were comparable in terms of age, sex, and hemoglobin levels. Serum LDH presentations were higher in positive IAT patients, response to corticosteroids was numerically higher in patients with negative IAT (54%) than those with positive IAT (33%), and after tapering steroids, patients with a positive IAT had higher rates of relapses compared with those with negative IAT. Positive ANA was found only in IAT-positive patients (25%), which was statistically significant.

Conclusion: An association between baseline IAT positivity and lower rates of complete response was observed in PWAIHA patients. The presence of IAT serves as a prognostic indicator and aids in the decision-making process regarding treatment options. Furthermore, positive IAT results are linked to a higher prevalence of ANA positivity.