Threshold for diagnosing hypertension by automated office blood pressure using randomsample population data

Objective: Manual office blood pressure (BP) is still recommended for diagnosing hypertension. However, its predictive value is decreased by errors in measurement technique and the white-coat effect. The errors can be eliminated by automated office BP (AOBP) measurement taking multiple readings with the participant resting quietly alone. Therefore, use of AOBP in clinical practice requires a threshold value for hypertension diagnosis. The aim of the present study was to determine an AOBP threshold corresponding to the 140/90mmHg manual office BP using data from a large random population sample. Methods: In 2145 participants (mean age 47.3-11.3 years) randomly selected from a Brno population aged 25- 64 years, BP was measured using manual mercury and automated office sphygmomanometers. Results: Manual SBP (mean difference 6.39-9.76 mmHg) and DBP (mean difference 2.50-6.54 mmHg) were higher than the automated BP. According to polynomial regression, automated systole of 131.06 (95% confidence interval 130.43-131.70) and diastole of 85.43 (95% confidence interval 85.03-85.82) corresponded to the manual BP of 140/90 mmHg. Using this cut-off, the whitecoat hypertension was present in 24% of participants with elevated manual BP, whereas 10% had masked hypertension and 11% masked uncontrolled hypertension. In individuals with masked uncontrolled hypertension, only AOBP was associated with the urinary albumin-creatinine ratio, whereas there was no association with manual BP. Conclusion: AOBP of 131/85mmHg corresponds to the manual BP of 140/90 mmHg. This value may be used as a threshold for diagnosing hypertension using AOBP. However, outcome-driven studies are required to confirm this threshold.