J Clin Hypertens (Greenwich). 2011;13:821–828. ©2011 Wiley Periodicals, Inc.

Electronic medical records (EMRs) allow for real-time access to blood pressure (BP) information on a population basis and improve identification and treatment of individuals with hypertension. Despite the potential uses of the data available from EMRs, relatively little research has examined the reliability of this data. To address this gap, the authors examined the reliability of BP taken at primary care visits and recorded in an EMR with those taken at a research study visit at which standard protocols were used to measure BP among all adults as well as by sex and age. Systolic BP (SBP) averaged 3.7 (17.3) points and diastolic BP (DBP) was 2.8 (10.6) points lower in the EMR than in the study visit across age and sex groups, with all differences statistically significant. For this cohort of patients with a diagnosis of hypertension, there was moderate correlation between BP measurements taken in clinic and at research. However, BP control for individuals, as defined by an SBP <140 mm Hg and DBP 90 mm Hg, differed by almost 25%. Known variability of BP and clinic procedures for measuring and recording BP may account for these differences.