Significance of quantitation of autoantibodies in the eluate of sensitized red cells in warm autoimmune hemolytic anemia

Abstract

Background: Concentrated autoantibodies obtained by elution can be subjected for total serological characterization including their quantitation. The present study was performed to correlate the quantity of immunoglobulin (Ig) G (IgG) autoantibodies in eluate with direct antiglobulin test (DAT) reactivity and markers of in vivo hemolysis in warm autoimmune hemolytic anemia (WAIHA). Methods: Detailed autoantibody characterization was performed on 34 samples with regards to antibody class, IgG subclass, DAT dilution and quantification study on eluate. Cold acid elution was performed on the DAT positive red cells and quantitation of IgG in eluates was done using ELISA. Number of IgG molecules eluted per RBC was calculated using Avogadro's number. Results: We observed a significant correlation between the concentration of IgG in eluate and DAT strength (r = 0.53, P = 0.014), hemoglobin (Hb)(r = -0.41, P = 0.04), serum bilirubin (r = 0.67, P = 0.000) and serum lactate dehydrogenase (LDH) (r = 0.50, P = 0.02). The number of IgG molecules/RBC also correlated significantly with the DAT strength (r = 0.69, P = 0.001) as well as DAT dilutions (r = 0.53, P = 0.004). Conclusions: Quantification of autoantibodies in eluate in WAIHA helps to assess the severity of the disease and plan appropriate management.