Comparability of Automated Office Blood Pressure to Daytime 24-Hour Ambulatory Blood Pressure.

BACKGROUND: Clinical practice guidelines endorse automated office blood pressure (AOBP) measurement as the preferred in-office measurement modality. However, recent data indicate that this method may underestimate daytime ambulatory BP. The objective of this study was to further assess the comparability of mean AOBP and daytime ambulatory BP in clinical practice. METHODS: A retrospective cross-sectional chart review was conducted of 96 consecutive patients referred from primary or specialty care practices to a tertiary care ambulatory BP monitoring service. Six AOBP readings were taken using an appropriately cuffed BpTRU (BpTRU Medical Devices, Coquitlam, Canada) device on the nondominant arm and no rest period (first reading discarded). Twenty-four-hour ambulatory BP monitoring was then performed. Between-group means were compared with paired t tests. The proportion of patients with differences of ≥ 5, 10, and 15 mm Hg was tabulated. RESULTS: Mean age was 52.6 ± 16.7 years, 60% were women, and 79% had previously diagnosed hypertension. Mean AOBPs were 130.8 ± 15.5/82.3 ± 10.7 mm Hg, and mean daytime ambulatory BPs were 142.8 ± 14.9/83.9 ± 11.2 mm Hg (difference of -11.9 ± 13.5/-1.6 ± 7.6; P < 0.001 for systolic BP and P < 0.04 for diastolic BP). Between-group differences were greater in patients with previous hypertension and in those with daytime ambulatory BP levels ≥ 135 mm Hg. The proportions of patients with systolic or diastolic BP differences of ≥ 5, 10 and 15 mm Hg were 89%, 52%, and 33%, respectively. CONCLUSIONS: Mean AOBP underestimates daytime ambulatory BP. Variability between the 2 methods is high. These findings do not support the premise that AOBP closely approximates daytime ambulatory BP.

An Assessment of the Accuracy of Home Blood Pressure Monitors When Used in Device Owners.

OBJECTIVE: To examine the accuracy of home blood pressure (BP) devices, on their owners, compared to auscultatory reference standard BP measurements. METHODS: Eighty-five consecutive consenting subjects ≥18 years of age, who owned an oscillometric home BP device (wrist or upper-arm device), with BP levels between 80-220/50-120 mm Hg, and with arm circumferences between 25-43 cm were studied. Pregnancy and atrial fibrillation were exclusion criteria. Device measurements from each subject's home BP device were compared to simultaneous 2-observer auscultation using a mercury sphygmomanometer. Between-group mean comparisons were conducted using paired t-tests. The proportion of patients with device-to-auscultatory differences of ≥5, 10, and 15 mm Hg were tabulated and predictors of systolic and diastolic BP differences were identified using linear regression. RESULTS: Mean age was 66.4 ± 11.0 years, mean arm circumference was 32.7 ± 3.7 cm, 54% were female and 78% had hypertension. Mean BPs were 125.7 ± 14.0/73.9 ± 10.4 mm Hg for home BP devices vs. 129.0 ± 14.7/72.9 ± 9.3 for auscultation (difference of -3.3 ± 7.3/0.9 ± 6.1; P values <0.0001 for systolic and 0.17 for diastolic). The proportion of devices with systolic or diastolic BP differences from auscultation of ≥5, 10, and 15 mm Hg was 69%, 29%, and 7%, respectively. Increasing arm circumference was a statistically significant predictor of higher systolic (parameter estimate 0.61 per cm increase; P value 0.004) and diastolic (0.38; 0.03) BP. CONCLUSIONS: Although mean differences from 2-observer auscultation were acceptable, when tested on their owners, most home BP devices were not accurate to within 5 mm Hg. Ensuring acceptable accuracy of the device-owner pairing should be prioritized.