Agreement between Medicare pharmacy claims, self-report, and medication inventory for assessing lipid-lowering medication use.

BACKGROUND: Medicare claims have been used to study lipid-lowering medication (LLM) use among US adults.
METHODS: We analyzed the agreement between Medicare claims for LLM and LLM use indicated by self-report during a telephone interview and, separately, by a medication inventory performed during an in-home study visit upon enrollment into the REasons for Geographic And Racial Differences in Stroke (REGARDS) study. We included REGARDS participants ≥65 years enrolled in 2006-2007 with Medicare pharmacy benefits (Part D) from 120 days before their telephone interview through their medication inventory (n = 899).
RESULTS: Overall, 39.2% and 39.5% of participants had a Medicare claim for an LLM within 120 days prior to their interview and medication inventory, respectively. Also, 42.7% of participants self-reported using LLMs, and 41.8% had an LLM in their medication inventory. The Kappa statistic (95% confidence interval [CI]) for agreement of Medicare claims with self-report and medication inventory was 0.68 (0.63-0.73) and 0.72 (0.68-0.77), respectively. No Medicare claims for LLMs were present for 22.1% (95%CI: 18.1-26.6%) of participants who self-reported taking LLMs and 18.9% (15.1-23.3%) with LLMs in their medication inventory. Agreement between Medicare claims and self-report was lower among Black male individuals (Kappa = 0.34 [95%CI: 0.14-0.54]) compared with Black female individuals (0.70 [0.61-0.79]), White male individuals (0.65 [0.56-0.75]), and White female individuals (0.79 [0.72-0.86]). Agreement between Medicare claims and the medication inventory was also low among Black male individuals (Kappa = 0.48 [95%CI: 0.29-0.66]).
CONCLUSIONS: Although substantial agreement exists, many Medicare beneficiaries who self-report LLM use or have LLMs in a medication inventory have no claims for these medications.