Human platelet associated IgG (PAIgG) levels were determined by competitive micro enzyme-linked immunosorbent assay (ELISA) with adequate reproducibility, recovery, and liniality for the sample dilution test. The washed platelet suspensions were prepared with the phosphate buffer saline containing 0.1% bovine serum albumin, and determined the IgG levels. The ELISA was done with 96 well microplate coating a purified human IgG. The horseradish peroxidase conjugated anti-human IgG antibody was incubated simultaneously with the sample, and colored with o-phenylenediamine. The normal PAIgG range (Mean ±SD) was 16.1±3.6ng/107P1 (n=69), and no difference was found in either sex. The levels were elevated in patients with idiopathic thrombocytopenic purpura (528.4±2132.6 ng/107) P1, n=63), aplastic anemia (243.4±262.4 ng/107 PI, n=23), iron deficiency anemia (19.0±7.4 ng/107 Pl, n=10), acute lymphatic leukemia (53.4±43.2 ng/107 Pl, n=6), acute myelogeneous leukemia (55.3±46.3 ng/107 Pl, n=8), chronic myelogeneous leukemia (61.6 ±41.4ng/107Pl, n=13), polycythemia vera (81.3±100.5ng/107Pl, n=9), and multiple myeloma (111.9±92.4 ng/107 Pl, n=10). After the storage of nine samples at 4°C for 6 days, the PAIgG level of each sample was elevated. Mean value of the nine samples was increased to 161% of that of samples stored at 4°C for a day. The mean platelet population was decreased to 50% of its beginning when the five platelet suspensions were stored at 4°C for 6 days.
