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

Abstract

BackgroundClinical 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. MethodsA 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. ResultsMean 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. ConclusionsMean 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.