Results for serum and plasma compared in 15 selected radioassays.

We evaluated the results for serum vs. plasma samples for 15 selected radioassay procedures, using 19 manufacturers' kits. Blood samples were collected with heparin, oxalate-fluoride, or ethylenediaminetetraacetate anticoagulants and compared with serum samples. Differences were demonstrated between serum and plasma which may be of sufficient magnitude to alter clinical interpretation of the results. Assays also demonstrated significant differences based on the kit manufacturer and procedure used.