PFA-100 (TM) system: A new method for assessment of platelet dysfunction

The PFA-100(TM) system is a platelet function analyzer designed to measure platelet-related primary hemostasis. The instrument uses two disposable car tridges: a collagen/epinephrine (CEPI) and a collagen/ADP (CADP) cartridge. Previous experience has shown that CEPI cartridges detect qualitative plat elet defects, including acetylsalicylic acid (ASA)-induced abnormalities, w hile CADP cartridges detect only thrombocytopathies and not ASA use. In thi s seven-center trial, 206 healthy subjects and 176 persons with various pla telet-related defects, including 127 ASA users, were studied. The platelet function status was determined by a platelet function test panel. Compariso ns were made as to how well the defects were identified by the PFA100(TM) s ystem and by platelet aggregometry. The reference intervals for both cartri dges, testing the 206 healthy subjects, were similar to values described in smaller studies in the literature [mean closure time (CT) 132 s for CEPI a nd 93 s for CADP]. The use of different lot numbers of cartridges or duplic ate versus singleton testing revealed no differences. Compared with the pla telet function status, the PFA-100(TM) system had a clinical sensitivity of 94.9% and a specificity of 88.8%. For aggregometry, a sensitivity of 94.3% and a specificity of 88.3% were obtained. These values are based on all 38 2 specimens. A separate analysis of sensitivity by type of platelet defect, ASA use versus congenital thrombocytopathies, revealed for the PFA-100(TM) system a 94.5% sensitivity in identifying ASA users and a 95.9% sensitivit y in identifying the other defects. For aggregometry, the values were 100% for ASA users and 79.6% for congenital defects. Analysis of concordance bet ween the PFA-100(TM) system and aggregometry revealed no difference in clin ical sensitivity and specificity between the systems (p > 0.9999). The over all agreement was 87.5%, with a Kappa index of 0.751. The two tests are thu s equivalent in their ability to identify normal and abnormal platelet defe cts. Testing 126 subjects who took 325 mg ASA revealed that the PFA-100(TM) system (CEPI) was able to detect 71.7% of ASA-induced defects with a posit ive predictive value of 97.8%. The overall clinical accuracy of the system, calculated from the area under the ROC curve, was 0.977. The data suggest that the PFA-100(TM) system is highly accurate in discriminating normal fro m abnormal platelet function. The ease of operation of the instrument makes it a useful tool to use in screening patients for platelet-related hemosta sis defects.