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

Abstract

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 B2 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 STxB2 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 STxB2 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.

Keywords: NSAID; aspirin; cardiovascular prevention; compliance; nonsteroidal anti-inflammatory drug; thromboxane B2.

Figure 1.

Comparison of serum thromboxane B2 levels in patients based on aspirin and possible interfering medication use. The boxplot shows the median (line), the 25th and 75th percentiles (box), and the upper and lower values within 1.5 times the interquartile range beyond the 25th and 75th percentile (whiskers). The dots represent outliers. ASA, aspirin; INT, possible interfering medication.

Figure 2.

Receiver–operating characteristic curve of serum thromboxane B₂ levels and aspirin use. The c-statistic is 0.97.