Detecting low antiplatelet response depends on the test used; LTA and VerifyNow showed moderate correlation, while TEG correlated poorly, and low aspirin response was found on 6 and 2 occasions.
Cohort (n=33)
Do different platelet function tests (LTA, VerifyNow, TEG) yield consistent results in detecting low response to aspirin and clopidogrel in post-PCI patients?
The detection of low response to clopidogrel and aspirin in post-PCI patients is highly dependent on the specific platelet function assay used, with significant intra-patient variability over time.
BACKGROUND: A reduced response to aspirin and clopidogrel predicts ischemic events, but reliable tests are needed to identify low responders. We compared 3 platelet-function tests during long-term dual treatment with aspirin and clopidogrel. METHODS: Patients who underwent a percutaneous coronary intervention and were receiving a combination of 325 mg/day aspirin and 75 mg/day clopidogrel were followed for 1 year. Blood was sampled 5 times during this period for 3 tests: light transmission aggregometry (LTA) assay, with 5.0 micromol/L ADP or 1.0 mmol/L arachidonic acid (AA) used as an agonist; VerifyNow assay, with the P2Y(12) or aspirin cartridge (Accumetrics); and thrombelastography (TEG), stimulated by 2.0 micromol/L ADP or 1.0 mmol/L AA. RESULTS: Twenty-six of 33 patients completed all scheduled visits. A low response to clopidogrel was found in a few patients at variable frequencies and at different visits, depending on the method and criteria used. We found a moderate correlation between the LTA (ADP) and VerifyNow (P2Y(12) cartridge) results, but the TEG (ADP) results correlated poorly with the LTA and VerifyNow results. A low response to aspirin was found with the VerifyNow (aspirin cartridge) and TEG (AA) methods on 6 and 2 occasions, respectively, but not with the LTA (AA) method, except for 1 occasion caused by probable noncompliance. CONCLUSIONS: Detecting a low response to clopidogrel depends largely on the method used. Which method best predicts ischemic events remains uncertain. A low response to aspirin is rare with AA-dependent methods used at the chosen cutoffs. In some patients, the response to clopidogrel or aspirin may be classified differently at different times, even with the same method.
Madsen et al. (2010) conducted a cohort in Percutaneous coronary intervention (n=33). Platelet-function tests (LTA, VerifyNow, TEG) was evaluated on Correlation between platelet-function tests for detecting low response to aspirin and clopidogrel. Detecting low antiplatelet response depends on the test used; LTA and VerifyNow showed moderate correlation, while TEG correlated poorly, and low aspirin response was found on 6 and 2 occasions.