Validity of Self-Reported Medication Use Compared With Pharmacy Records in a Cohort of Older Women: Findings From the Women's Health Initiative

Inaccurate self-reported data on medication exposure lead to less reliable study findings. From 2013 to 2015, we assessed the validity of information on medication use collected via a mailed medication inventory among 223 Women's Health Initiative participants who were members of a health-care delivery system. Self-reported information on medication use was compared with pharmacy records for statins, calcium channel blockers, β-blockers, and bisphosphonates. We assessed sensitivity, specificity, and positive predictive value (PPV) for current medication use. We assessed agreement on duration of use (<2, 2, 3, 4, or ≥5 years) by means of the weighted κ statistic. The mean age of participants was 77 years. Statins, β-blockers, and calcium channel blockers were each reported by over 15% of women, and bisphosphonates were reported by 4.5%. Compared with pharmacy records, the sensitivity, specificity, and PPV for self-reported use of statins, β-blockers, and calcium channel blockers were all 95% or greater. The sensitivity and PPV for bisphosphonate use were both 80% (95% confidence interval: 44, 97), and specificity was 99% (95% confidence interval: 97, 100). The κ statistic for duration of use was 0.87 or greater for all 4 medication classes. Compared with pharmacy records, self-reported information on current medication use and duration of use collected via mailed medication inventory among older women had almost perfect agreement for use of statins, β-blockers, and calcium channel blockers.