Underreporting high-risk prescribing among Medicare Advantage plans: a cross-sectional analysis.

Background: Although Medicare Advantage plans are required to report clinical performance using Healthcare Effectiveness Data and Information Set (HEDIS) quality indicators, the accuracy of plan-reported performance rates is unknown.

Objective: To compare calculated and reported rates of high-risk prescribing among Medicare Advantage plans.

Design: Cross-sectional comparison.

Setting: 172 Medicare Advantage plans.

Patients: A random sample of beneficiaries in 172 Medicare Advantage plans in 2006 (n = 177,227) and 2007 (n = 173,655).

Measurements: Plan-reported HEDIS rates of high-risk prescribing among elderly persons were compared with rates calculated from Medicare Advantage plans' Part D claims by using the same measure specifications and source population.

Results: The mean rate of high-risk prescribing derived from Part D claims was 26.9% (95% CI, 25.9% to 28.0%), whereas the mean plan-reported rate was 21.1% (CI, 20.0% to 22.3%). Approximately 95% of plans underreported rates of high-risk prescribing relative to calculated rates derived from Part D claims. The differences in the calculated and reported rates negatively affected quality rankings for the plans that most accurately reported rates. For example, the 9 plans that reported rates of high-risk prescribing within 1 percentage point of calculated rates were ranked 43.4 positions lower when reported rates were used instead of calculated rates. Among 103,680 individuals present in both the sample of Part D claims and HEDIS data in 2006, Medicare Advantage plans incorrectly excluded 10.3% as ineligible for the HEDIS high-risk prescribing measure. Among those correctly included in the high-risk prescribing denominator, the reported rate of high-risk prescribing was 21.9% and the calculated rate was 26.2%.

Limitation: A single quality measure was assessed.

Conclusion: Medicare Advantage plans underreport rates of high-risk prescribing, suggesting a role for routine audits to ensure the validity of publicly reported quality measures.

Primary Funding Source: Health Assessment Lab and National Institute on Aging.