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

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.