Utility of adsorption techniques in serological evaluation of warm autoimmune haemolytic anaemia

Various adsorption techniques are available to remove serum autoantibodies and subsequently detect the underlying alloantibody in previously transfused patients with autoimmune haemolytic anaemia. We planned to establish a suitable adsorption technique in our transfusion service which can remove all autoantibodies and detect underlying alloantibodies rapidly, cheaply and effectively.

We evaluated 71 direct antiglobulin test-reactive patients with warm AIHA over a period of 20 months. Twenty-three of these 71 patients who had a previous history of blood transfusion or pregnancy and were confirmed carriers of autoantibodies (indirect antiglobulin test-reactive) were considered for the adsorption study. Depending on the adequacy of samples, history of blood transfusion and severity of anaemia either autoadsorption or alloadsorption or both using polyethylene glycol (PEG) or low ionic strength saline (LISS)-papain were performed.

Underlying alloantibodies were detected in 7 of the 23 patients (30.4%) and all these were specific to Rhesus antigens. The mean number of alloadsorptions for complete autoantibody removal using PEG was 1.43 which was significantly lower than the 3.9 using the LISS-papain method (p<0.05). The mean time required by PEG alloadsorption and LISS-papain alloadsorption for autoantibody removal was 93.6 minutes and 177.7 minutes, respectively (p<0.05). Discordant results were not observed in any case and identical alloantibodies were detected by both the techniques.

We found that the PEG method is a rapid, cheap and effective way to remove autoantibodies and detect underlying alloantibodies.