Reactivity of a transient autoantibody inhibited by ionized calcium

A 53-year-old female suffering from severe anaemia following falciparum malaria required blood transfusion. Her blood specimen in EDTA showed strong autoagglutination giving problems in the preliminary grouping by a slide test. She was grouped, however, as B Rh-D positive without difficulty by the cell and serum groupings done using clotted blood. Two units of B Rh-D positive blood compatible with the patient's serum were transfused without untoward reaction. The patient's blood collected a fresh in different anticoagulants showed autoagglutination in the plasma with EDTA or citrate, but not in heparin collection or in serum, indicating a possible role of ionized calcium as an inhibitor of reactivity. Addition of 0.02 M calcium chloride solution to the plasma remarkably weakened the strength of agglutination, evidently supporting this hypothesis. Autoantibody, identified as anti-Pra, was transient in nature and possibly associated with the malarial infection, as neither the antibody nor the malarial parasites were detected in her blood in follow up studies four months later.