Abstract
This is a celebratory reprint of a historical paper published in STH in 1998. The
original Abstract follows.
The PFA-100 system is a platelet function analyzer designed to measure platelet-related
primary hemostasis. The instrument uses two disposable cartridges: a collagen/epinephrine
(CEPI) and a collagen/ADP (CADP) cartridge. Previous experience has shown that CEPI
cartridges detect qualitative platelet defects, including acetylsalicylic acid (ASA)-induced
abnormalities, while CADP cartridges detect only thrombocytopathies and not ASA use.
In this seven-center trial, 206 healthy subjects and 176 persons with various platelet-related
defects, including 127 ASA users, were studied. The platelet function status was determined
by a platelet function test panel. Comparisons were made as to how well the defects
were identified by the PFA-100 system and by platelet aggregometry. The reference
intervals for both cartridges, testing the 206 healthy subjects, were similar to values
described in smaller studies in the literature (mean closure time [CT] of 132 seconds
for CEPI and 93 seconds for CADP). The use of different lot numbers of cartridges
or duplicate versus singleton testing revealed no differences. Compared with the platelet
function status, the PFA-100 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 382 specimens. A separate analysis of sensitivity
by type of platelet defect, ASA use versus congenital thrombocytopathies, revealed
for the PFA-100 system a 94.5% sensitivity in identifying ASA users and a 95.9% sensitivity
in identifying the other defects. For aggregometry, the values were 100% for ASA users
and 79.6% for congenital defects. Analysis of concordance between the PFA-100 system
and aggregometry revealed no difference in clinical sensitivity and specificity between
the systems (p > 0.9999). The overall agreement was 87.5%, with a Kappa index of 0.751. The two
tests are thus equivalent in their ability to identify normal and abnormal platelet
defects. Testing 126 subjects who took 325 mg ASA revealed that the PFA-100 system
(CEPI) was able to detect 71.7% of ASA-induced defects with a positive predictive
value of 97.8%. The overall clinical accuracy of the system, calculated from the area
under the receiver operating characteristic curve, was 0.977. The data suggest that
the PFA-100 system is highly accurate in discriminating normal from abnormal platelet
function. The ease of operation of the instrument makes it a useful tool to use in
screening patients for platelet-related hemostasis defects.
Keywords
PFA-100 system - thrombocytopathies - von Willebrand disease - aspirin - platelet
aggregometry - bleeding time
