Plasma Levels of Platelet Factor 4 Measured by Radioimmunoassay

Publisher Website
Google Scholar
Abstract
A radioimmunoassay was developed to measure [human] platelet factor 4 (PF4) in biological fluids in vitro and in vivo. The assay was highly specific for PF4 and had a sensitivity of 0.08 ng/assay tube and 1.6 ng/ml of plasma. The preparation of plasma for the measurement of in vivo levels of PF4 required the use of an anticoagulant containing EDTA, theophylline and prostaglandin E1, the immediate cooling of the blood and high speed or prolonged centrifugation to reduce platelet contamination. Plasma levels of PF4 were normally between 4-24 ng/ml with a median of 7.4 ng/ml. Plasma PF4 levels were markedly increased during cardiopulmonary bypass surgery with shortened 51Cr-labeled platelet survival times and during arterial thrombosis. Despite similarly shortened platelet survival times, the level of PF4 was normal in immune thrombocytopenia. Elevations of plasma PF4 levels were found following surgery, acute myocardial infarction and frequently during acute infections and in inflammatory states. Normal levels were usual in disseminated malignancy, severe hepatic and renal disease and chronic arterial disease. The measurement of PF4 is a useful addition to the study of platelet pathophysiology. It is apparent that raised levels are not specific for thromboembolic disease and similarly platelet destruction is not invariably associated with abnormally increased plasma PF4 levels.