Improved radioimmunoassay of platelet factor 4 and beta-thromboglobulin in plasma.

We describe rapid radioimmunoassays for both platelet factor 4 (PF-4) and beta-thromboglobulin (beta-TG) on the same plasma sample with use of pre-precipitated second antibody for the separation step. The assays are sensitive (B/B0 of 90% is obtained with 30 pg PF-4 and 100 pg beta-TG), specific, accurate, and reproducible. Labeled antigens are highly immunogenic, stable, and require no initial or periodic purification. Both assays require less than five hours for precount incubation times and can easily be completed in one day. Normal plasma values for PF-4 and beta-TG were 2.98 ng/ml and 25.83 ng/ml, respectively.