Rethinking Blood Pressure Quality Measurement: Accounting for Seasonal Variation in Value-Based Care

Abstract

Blood pressure (BP) control is a core quality metric in value-based care (VBC). The Healthcare Effectiveness Data and Information Set (HEDIS) Controlling High Blood Pressure (CBP) measure uses the final BP reading of the calendar year, a method that overlooks well-documented seasonal variation—BP declines in summer and rises in winter. We evaluated the impact of this pattern on measured performance in a large health system. We conducted a retrospective analysis of monthly BP control rates (July 2019 to December 2025) across the Jefferson Health-Lehigh ambulatory network, totaling 78 months and approximately 7.6 million patient-months. Summer (June to August) and winter (December to February) rates were compared using paired t-tests and ordinary least square regression with seasonal adjustment. Year-end performance was assessed using both the HEDIS final-reading (December rate) and a rolling Q4 average (October to December mean). Standard VBC quality improvement initiatives with Q4 intensification were in place. BP control rates were significantly higher in summer (75.2%; 95% confidence interval [CI]: 73.5%–77.0%) than winter (73.1%; 95% CI: 71.2%–75.1%), a 2.1-percentage-point difference (paired t = 5.13, P = 0.002). This pattern was consistent across all 7 years. Within-year peak-to-trough amplitude averaged 2.8 percentage points in nonpandemic years. The rolling Q4 average exceeded the December-only rate in all years, with differences of 0.06–0.59 percentage points, reclassifying 60–520 additional patients as controlled annually. Seasonal BP variation is robust and inadequately addressed by current quality measures. Multi-reading or seasonally adjusted methods would improve measurement accuracy and fairness. Engagement with NCQA and CMS to pilot redesigned measures is recommended.