Conventional versus automated measurement of blood pressure in the office (CAMBO) trial

Background: Effective strategies to identify office-induced hypertension in routine clinical practice are required to improve diagnosis and management of hypertension. Objective: To compare the quality and accuracy of automated office blood pressure (AOBP) measurement using the BpTRU device with manual office blood pressure (MOBP) in routine clinical practice using awake ambulatory blood pressure (AABP) as the gold standard. Methods: Primary care practices in Eastern Canada were allocated by cluster randomization to use of AOBP (36 practices, 52 physicians) or to MOBP (31 practices, 36 physicians) in patients with systolic hypertension. The last routine MOBP reading pre-enrolment was compared to the blood pressure (BP) at the first visit after enrolment and after 2 years of follow-up. The primary outcome measure was the mean difference between the AABP and MOBP versus AOBP. Results: The mean (95% confidence interval) decrease in systolic BP from pre- to post-enrolment was greater (P < 0.001) at the first visit in the 252 AOBP patients [-14.3 (-16.6, -12.0)] compared to the 209 MOBP patients [-8.0 (-2.2, -5.8)]. At Year 2, AOBP decreased by -16.3 (-18.6, -14.1) compared to a decrease in MOBP of -12.4 (-14.7, -10.1) (P = 0.02). The mean difference between systolic AABP and MOBP at the first post-enrolment office visit [-7.3 (-9.7, -4.9)] was greater (P < 0.001) than the difference for AOBP [-1.8 (-4.0, 0.4)]. At Year 2, these differences were -5.2 (-7.5, -3.0) for MOBP and -2.8 (-4.9, -0.7) for AOBP (P = 0.13). Conclusions: AOBP virtually eliminated office-induced hypertension. The decrease in MOBP was attributed to participation in a research study and not to any specific intervention.