Platelet factor 4 radioimmunoassay.

(a) Identification. A platelet factor 4 radioimmunoassay is a device used to measure the level of platelet factor 4, a protein released during platelet activation by radioimmunoassay. This device measures platelet activiation, which may indicate a coagulation disorder, such as myocardial infarction or coronary artery disease. (b) Classification. Class II (performance standards). [45 FR 60625, Sept. 12, 1980; 46 FR 14890, Mar. 3, 1981]