There are alternative aspirin-specific methodologies as well that test for resistance. For example, the 11-dehydrothromboxane B2 (11-dTXB2)test. This compound is a stable, inactive metabolite of thromboxane A2 and an in vivo indicator of platelet activity.
If 11-dTXB2 is elevated in a urine sample from a patient receiving antiplatelet aspirin therapy, aspirin resistance may be indicated, since aspirin is intended to inhibit thromboxane A2 production. The elevated level of 11-dTXB2 indicates a continued hypercoagulable state and the patient may be at increased risk for an ischemic cardiovascular event. If the test result is elevated, alternative anti-thrombotic or antiplatelet therapies should be considered.
The AspirinWorks® test system is an enzyme-linked immunosorbent assay (ELISA) for 11-dTXB2. This test system will be discussed next.