Monitoring aspirin therapy with the Platelet Function Analyzer-100.
OBJECTIVE
Low platelet response to aspirin has been reported to be associated with a high incidence of vascular events. The reported prevalence of aspirin low-responsiveness varies, which may be explained by poor reproducibility of the methods used to evaluate aspirin response and low compliance. The Platelet Function Analyzer-100 (PFA-100) is a commonly used platelet function test. We aimed to assess the reproducibility of the PFA-100 and the agreement with optical platelet aggregometry (OPA) in healthy volunteers and in patients with coronary artery disease (CAD) treated with low-dose aspirin.


METHODS
Twenty-one healthy volunteers and 43 patients with CAD took part in the study. During treatment with aspirin 75 mg daily, all participants had platelet function assessed in duplicate with the PFA-100 and OPA on 4 consecutive days. Additionally, platelet function was assessed before aspirin treatment in healthy subjects. Serum-thromboxane B(2) (S-TxB(2)) was measured to assess compliance.


RESULTS
In healthy volunteers not receiving aspirin, duplicate measurements resulted in coefficients of variation (CV) of 7.9 % for the PFA-100 and 5.2 % for OPA. During aspirin treatment, CVs were significantly higher (healthy volunteers: PFA-100: 15.6 %, OPA: 19.2 %; patients: PFA-100: 26.6 %, OPA: 16.8 %). Two of the 64 participants were classified as aspirin low-responders with both methods, indicating poor agreement (Kappa coefficient 0.05). Compliance was excellent, as S-TxB(2) was completely inhibited in all participants.


CONCLUSIONS
Aspirin treatment affects the reproducibility of both PFA-100 and OPA. This imprecision should be considered carefully if the methods are used for monitoring aspirin treatment. Additionally, these methods do not identify the same individuals as being aspirin low-responders.
Mortensen
Jette
J
Department of Cardiology, Aarhus University Hospital Skejby, Aarhus, Denmark.
Poulsen
Tina Svenstrup
TS
Grove
Erik Lerkevang
EL
Refsgaard
Jens
J
Nielsen
Helle Ladefoged
HL
Pedersen
Susanne Bendesgaard
SB
Thygesen
Sofie Sommer
SS
Hvas
Anne-Mette
AM
Kristensen
Steen Dalby
SD
D000328:Adult; D016718:Arachidonic Acid / Q000494:pharmacology; D001241:Aspirin / Q000627:therapeutic use*; D003324:Coronary Artery Disease / Q000188:drug therapy; D005260:Female; D006262:Health; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D010974:Platelet Aggregation / Q000187:drug effects; D010979:Platelet Function Tests / Q000295:instrumentation*
D016718:Arachidonic Acid; D001241:Aspirin