Confirmation of reported aspirin use in community studies: Utility of serum thromboxane B₂ measurement

Aspirin (ASA) is recommended for the prevention of cardiovascular disease; however, the compliance is low. Reported use may not reflect actual use. Serum thromboxane B₂ (STxB₂) measurement was evaluated to validate reported ASA use. Males aged 45 to 79 years and females aged 55 to 79 years completed a survey and STxB₂ measurement (Thromboxane B ₂ EIA Kit; Cayman Chemical, Ann Arbor, Michigan). The 107 patients were grouped by use of ASA (56 ASA+ and 51 ASA-) and possible interfering medications (INT) such as nonsteroidal anti-inflammatory drugs. The STxB ₂ levels (ng/mL) were significantly lower in ASA users: ASA+ INT- 3.0 (0.7, 8.4), ASA+ INT+ 2.0 (0.8, 4.9), ASA- INT+ 176 (75, 390), and ASA- INT- 271 (199, 366). The INT use did not cause a significant difference in STxB ₂ levels. A STxB₂ cut point of 25 ng/mL had high sensitivity (94.1%) and specificity (91.1%) for ASA use. The STxB₂ was a reliable marker of ASA use and could be used to confirm ASA exposure in population-based health studies.