Aspirin Resistance Is Relatively Common Phenomenon
But poor compliance may contribute to substantial number of apparent resistance cases
FRIDAY, Sept. 30 (HealthDay News) -- Aspirin resistance is common, but poor compliance may contribute to a substantial number of cases of apparent resistance, according to a study published in the October issue of Cardiovascular Therapeutics.
Jesse Dawson, M.D., from the University of Glasgow in the United Kingdom, and colleagues investigated the rate of aspirin-resistance and its correlation with poor therapy compliance. A total of 90 patients enrolled within 24 hours of ischemic stroke and 90 controls who received aspirin with no prior experience of a vascular event while on therapy were assessed for platelet function. Urine levels of aspirin metabolites were measured to verify compliance with therapy. Rates of resistance in stroke patients and controls were compared, and subgroup analysis for patients with objective confirmation of recent aspirin ingestion was performed. All patients claimed to be compliant.
The investigators identified 177 patients with complete platelet function tests. Resistance rates for cases and controls on one or more test, on platelet function analyzer (PFA)-100 testing only, on rapid PFA testing only, and in both tests were 34 versus 25 percent, 32 versus 18 percent, 18 versus 14 percent, and 14 versus 6 percent, respectively. Similar rates were found when only patients with objective evidence of recent aspirin ingestion were assessed, regardless of the resistance definition used.
"Data from our study suggest that aspirin resistance is a common phenomenon that merits further study, but that poor compliance may contribute in a substantial number of cases of apparent resistance," the authors write.