Study on anti-phospholipid antibodies in chronic idiopathic thrombocytopenic purpura.

We have developed a new solid phase enzyme immunoassay (EIA) for detec tion of anti-phospholipid antibodies in sera and platelet eluates from patients with idiopathic thrombocytopenic purpura (ITP). Antibodies against cardiolipin (CAR), phosphatidylinositol (PI) and phosphatidylserine (PS), not against phos phatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA) and sphyngomyelin (SM) were frequently found in the ITP patients' sera. Among 69 ITP patients examined, IgG class antibodies against CAR, PI and PS were de tected in 12, 10 and 9 patients and IgM class antibodies in 16, 18 and 13 patients, respectively. When platelet eluates were analysed instead of sera, anti-phos pholipid antibodies in IgG class were detected in 14 cases out of 58 patients (anti CAR 4, anti-PI 13 and anti-PS 5), while the antibodies of IgM class were found in only one case. Although severe thrombocytopenia was found in one ITP patient with the exceptionally high titer of anti-phospholipid antibody, there were no clear correlation between the platelet counts and the titers of anti-phospholipid antibodies in platelet eluates. Thus, it is suggested that anti-phospholipid anti bodies do not play a major role in pathogenesis of thrombocytopenia in spite of such a high incidence. There were no distinct differences in clinical and labora tory features between cases with and without anti-phospholipid antibodies. How ever, it was of great interest that 2 ITP patients with high titers of antibodies against all three phospholipids (CAR, PI and PS) presented unique complications such as deep vein thrombosis and lupus anticoagulant, a risk factor for thrombosis.