Differentiation of autoimmune thrombocytopenia from thrombocytopenia associated with immune complex disease: systemic lupus erythematosus, hepatitis-cirrhosis, and HIV-1 infection by platelet and serum immunological measurements

A method and approach are described to differentiate classic autoimmune thr ombocytopenia (ATP) from immune complex-associated thrombocytopenia in syst emic lupus (SLE), hepatitis/chronic liver disease (LIV-ITP) and HIV-1 relat ed thrombocytopenia (HIV-1-ITP). The platelet immunologic profile of IgG, C 3C4 and IgM was measured with a solid-phase ELISA, employing I-125-staphylo coccal protein A to detect indicator antibody binding. Polyethylene glycol was employed to precipitate immune complexes (PEG-IC). Platelet-associated IgG (PAIgG) was 2.8-, 5.6- and 5.8-fold higher in SLE, LIV-ITP and HIV-1-IT P patients respectively compared to ATP patients: platelet C3C4 was 3.2-, 4 .8- and 4.5-fold higher respectively; platelet IgM was 2.2-, 3.7- and 3.8-f old higher respectively; serum PEG-IC levels were 4.2-. 4.8- and 2.1-fold h igher respectively. With all parameters measured, there was no overlap betw een the 75th percentile for ATP patients and the 25th percentile for all th ree cohorts. The likelihood of having a platelet C3C4 level higher than the highest ATP level was 69% for SLE, 90% for LIV-ITP and 94% for HIV-1-ITP r espectively; with PEG-IC measurements the likelihood was 83%, 100% and 100% respectively Serum IgG, C3, C4, IgM and PEG-IC were examined for a possibl e relationship with platelet measurements, Except for a positive correlatio n between serum and platelet IgM in ATP, r=0.5, P<0.04, there was no positi ve correlation with any of the parameters measured, An inverse correlation was noted between PEG-IC level and platelet C3C4 in SLE, r=0.7, P<0.04. Thu s platelet immunologic profile and serum PEG-IC level measurements differen tiated classic ATP from immune complex-associated thrombocytopenias (SLE, L IV-ITP, HIV-1-ITP), Except for IgM measurements in ATP, platelet measuremen ts could not be attributed to their respective serum concentration.