Serological Characterisation of Auto-antibodies in Patients with Direct Antiglobulin Test Positive Autoimmune Haemolytic Anaemia at a Tertiary Care Teaching Hospital in Tirupati, India

Introduction: Haemolysis in Autoimmune Haemolytic Anaemia (AIHA) is a result of Immunoglobulin G (IgG) or Immunoglobulin M (IgM) auto-antibodies with or without complement components binding to the Red Blood Cell (RBC) surface and initiating its destruction. Serologic evidence is provided by autocontrol or Direct Antiglobulin Test (DAT). Diagnostic work-up is essential as the management depends on the antibody type. Characteristics of the bound antibody and the target antigen determine the degree of haemolysis. Serological characterisation in AIHA helps to differentiate into its various types which help the clinician to decide on the treatment to be given. Aim: To serologically characterise the auto-antibodies in patients with DAT positive AIHA at a tertiary care teaching hospital. Materials and Methods: This cross-sectional study was carried out in the Department of Transfusion Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India, from March 2019 to February 2020. A 40 consecutive patient samples were included in the study. Characterisation of antibody was done using polyspecific Anti-Human Globulin (AHG) reagent followed by mono-specific AHG reagent by gel method. If antibody was of IgG type, then the subclass was determined by a mono specific anti-IgG1 and anti-IgG3 gel card. Association between antibody types, subtype, and strength of DAT with severity of haemolysis were compared using Chi-square/Fisher’s-exact test. A p-value of less than 0.05 was considered statistically significant. Results: The total study population was 40 patients. The mean age of the study population was 45 years (range 13-78). Out of 40 patients, males were 30 (75%) and females were 10 (25%). The primary and secondary causes for AIHA include 4 (10%) and 36 (90%) respectively. Among 40 patients, 22 (55%) patients had IgG antibody alone, 17 (42.5%) patients had IgG antibody with combination of other antibodies and 1 (2.5%) had only complement (C3d). IgG1 was identified in 7 (18%) of patients, combination of IgG1 and IgG3 in 3 (7.7%). There was a significant association with IgG+combination (p-value=0.03), IgG1+IgG3 (p-value=0.029) and strength of reaction (p-value=0.003) with respect to severity of haemolysis. Conclusion: Presence of multiple antibodies, presence of IgG1 and IgG3 and with complement combination and presence of higher grading of reaction in gel column were associated with severity of haemolysis. We recommend that serological ch