Comparison of Blood Pressure Measurements from Clinical Practice and a Research Study At Kaiser Permanente Southern California

Background: Accurate blood pressure (BP) measurement is essential to identify and manage hypertension. Prior studies have reported a difference between BP measured in routine patient care and in research studies. We aimed to investigate the agreement between BP measured in routine care and research-grade BP in Kaiser Permanente Southern California, a large, integrated healthcare system with initiatives to standardize BP measurements during routine patient care visits. Methods: We included adults ≥65 years old with hypertension, taking antihypertensive medication, and participating in the Ambulatory Blood Pressure in Older Adults (AMBROSIA) study in 2019–2021. Clinic BP from routine care visits was extracted from the electronic health record. Research-grade BP was obtained by trained AMBROSIA study staff via an automatic oscillometric device. The mean difference between routine care and research-grade BP, limits of agreement, and correlation were assessed. Results: We included 309 participants (mean age 75 years; 54% female; 49% non-Hispanic white). Compared with measurements from routine care, mean research-grade systolic BP (SBP) was 0.1 mm Hg higher (95% CI: −1.5 to 1.8) and diastolic BP (DBP) was 0.4 mm Hg lower (95% CI: −1.6 to 0.7). Limits of agreement were −29 to 30 mm Hg for SBP and −21 to 20 mm Hg for DBP. The intraclass correlation coefficient was 0.42 (95% CI: 0.33 to 0.51) for SBP and 0.43 (95% CI: 0.34 to 0.52) for DBP. Conclusions: High within-person variation and moderate correlation were present between BP measured in routine care and following a research protocol suggesting the importance of standardized measurements.