The conventional versus automated measurement of blood pressure in the office (CAMBO) trial: masked hypertension sub-study

Objectives: To determine the prevalence of masked hypertension [normal office blood pressure (BP) with high awake ambulatory BP] using automated office BP (AOBP) or conventional manual office BP (MOBP) measurement in routine clinical practice. Methods: The prevalence of masked hypertension was evaluated on three consecutive visits during a median 6 months period in patients with systolic hypertension randomized to management with AOBP (n = 140) or continued conventional MOBP (n = 112) in routine primary care practice. AOBP was recorded using the automated BpTRU device with the patient resting alone in a quiet examining room. All patients underwent 24-h ambulatory BP monitoring. Results: The prevalence of masked hypertension on any one of three visits calculated using only SBP varied between 12 and 17% in the AOBP group compared with 19 and 22% in the MOBP group. Masked hypertension was present on both of the first two visits in 7 and 12% and on all three visits in 6 and 7% of AOBP and MOBP patients, respectively. The prevalence for masked hypertension based upon both SBP and DBP was similar being 11-15% for AOBP and 19-20% for MOBP patients on single visits, but decreased to 6 and 10% when readings from the first two visits were used and to 4 and 6% when all three visits were used for the AOBP and MOBP groups, respectively. Conclusion: The prevalence of masked hypertension is lower with AOBP compared with MOBP. The number of patients with masked hypertension decreases if the criteria for having this condition need to be met on multiple visits.