Low-dose aspirin increases aspirin resistance in patients with coronary artery disease.
OBJECTIVE
We sought to investigate the association of aspirin dose and aspirin resistance in stable coronary artery disease patients measured by a point-of-care assay.


METHODS
We studied 468 consecutive stable coronary artery disease patients in a referral cardiac center who were taking aspirin 80 to 325 mg daily for > or =4 weeks. The VerifyNow Aspirin (Ultegra RPFA-ASA, Accumetrics Inc, San Diego, Calif) was used to determine aspirin responsiveness. An aspirin reaction unit (ARU) > or =550 indicates the absence of aspirin-induced platelet dysfunction, based on correlation with epinephrine-induced light transmission aggregometry. Demographic and clinical data were collected to analyze the predictors of aspirin resistance.


RESULTS
Aspirin resistance was noted in 128 (27.4%) patients. Univariate predictors of aspirin resistance include elderly (P = 0.002), women (P <0.001), anemia (P <0.001), renal insufficiency (P = 0.009) and aspirin dose < or =100 mg (P = 0.004). Multivariate analysis revealed hemoglobin (odds ratio [OR] 0.6; 95% confidence interval [CI] 0.51 to 0.69; P <0.001) and aspirin dose < or =100 mg (OR 2.23; 95% CI 1.12 to 4.44; P = 0.022) to be independent predictors of aspirin resistance. Daily aspirin dose < or = 100 mg was associated with increased prevalence of aspirin resistance compared with 150 mg and 300 mg daily (30.2% vs 16.7% vs 0%, P = 0.0062).


CONCLUSIONS
A 100 mg or less daily dose of aspirin, which may have lower side effects, is associated with a higher incidence of aspirin resistance in patients with coronary artery disease. Prospective randomized studies are warranted to elucidate the optimal aspirin dosage for preventing ischemic complications of atherothrombotic disease.
Department of Medicine, The University of Hong Kong, Queen Mary Hospital, China.
Pui-Yin
PY
Lee
Wai-Hong
WH
Chen
William
W
Ng
Xi
X
Cheng
Jeanette Yat-Yin
JY
Kwok
Hung-Fat
HF
Tse
Chu-Pak
CP
Lau
D000368:Aged; D001241:Aspirin / Q000008:administration & dosage / Q000627:therapeutic use*; D003327:Coronary Disease / Q000097:blood / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D012189:Retrospective Studies
D006454:Hemoglobins; D010975:Platelet Aggregation Inhibitors; D001241:Aspirin