[Prevalence of laboratory aspirin resistance in 431 old patients]

To evaluate correlation between and agreement in light transmittance aggregation (LTA) and thromboelastography (TEG) in laboratory diagnosing aspirin resistance (AR), and to determine the prevalence of AR in old patients.

Patients in the Wanshoulu District of Beijing with ischemic atherothrombotic diseases were recruited. Inclusion criteria were age ≥ 65 years, and having received regular aspirin therapy (75-100 mg daily) for at least 4 weeks. On the basis of LTA assay, the definition of AR was taken as aggregation of ≥ 20% with AA (arachidonic acid), and of ≥ 70% with ADP (adenosine diphosphate). Aspirin-sensitivity was indicated by the absence of either of these criteria; aspirinsensitivity was indicated as both criteria being met. The definition of AR by TEG is ≥ 50% via AA-induced whole blood aggregation.

There were 13.69% prevalence of aspirin resistance for LTA using AA as the agonist, 30.16% prevalence of aspirin resistance for LTA using ADP as the agonist, and 23.67% prevalence of aspirin resistance for TEG using AA as the agonist. Results from these tests showed poor agreement (Kappa<0.4). However, by the method of LTA using AA and ADP as the agonists, prevalence of AR was 8.35%. By methods of AA-induced LTA and AA-induced TEG, prevalence of AR was 8.82%. Results from these two latter methods showed good agreement (Kappa = 0.793).

Combined methods, as described here, have good correlation and agreement in the assays of AR, and the results with them represent a realistic measure of the prevalence of AR. Prevalence of AR of elderly patients from Wanshoulu district of Beijing is about 9%.