Variability in performance measures for assessment of hypertension control.

BACKGROUND: Definitions of multiple performance measures exist for the assessment of blood pressure control; however, limited data on how these technical variations may affect actual measured performance are available.
METHODS: We evaluated patients with hypertension followed routinely by cardiologists at Duke University Health System from 2009 to 2010. Provider hypertension control was compared based on reading at the last clinic visit vs the average blood pressure across all visits. The impact of home blood pressure measurements and patient exclusions endorsed by the American Heart Association, the American College of Cardiology, and the Physician Consortium for Performance Improvement were evaluated using medical record reviews.
RESULTS: Among 5,552 hypertensive patients, the rate of blood pressure control based on last clinic visit was 69.1%; however, significant clinic-to-clinic variability was seen in serial clinic blood pressure measurements in individual patients (average 18 mm Hg). As a result, provider performance ratings varied considerably depending on whether a single reading or average blood pressure reading was used. The inclusion of home blood pressure measurements resulted in modestly higher rates of blood pressure control performance (+6% overall). Similarly, excluding patients who met guideline-recommended exclusion criteria increased blood pressure control rates only slightly (+3% overall). In contrast, excluding patients who were on 2 or more antihypertensive medications would have raised blood pressure control rates to 96% overall.
CONCLUSION: Depending on definitions used, overall and provider-specific blood pressure control rates can vary considerably. Technical aspects of blood pressure performance measures may affect perceived quality gaps and comparative provider ratings.