Platelet factor 4 activity and thromboembolic episodes

Platelet factor 4 activity was evaluated in 323 patients who had various diseases. High incidences (30% or more) of elevated levels of platelet factor 4 were found in patients with recent myocardial infarctions, recent episodes of thromboembolism, hepatic diseases, and low platelet counts. Three of the four patients who had prosthetic heart valves had markedly elevated platelet factor 4 activities. It appears that elevation of platelet factor 4 activity is associated with a high platelet turnover such as is seen in intravascular coagulation or thromboembolism. Determination of platelet factor 4 activity may be a valuable laboratory tool for the diagnosis of thromboembolism.