Reproducibility of masked hypertension among adults 30 years or older

OBJECTIVE: Masked hypertension (MH) refers to nonelevated office blood pressure (BP) with elevated out-of-office BP, but its reproducibility has not been conclusively established. We examined 1-week reproducibility of MH by home BP monitoring (HBPM) and ambulatory BP monitoring (ABPM). METHODS: We recruited 420 adults not on BP-lowering medication, with recent clinic BP between 120/80 and 149/95 mmHg. For main comparisons, participants with office average less than 140/90 mmHg were considered to have MH if awake ABPM average was 135/85 mmHg or higher; they were considered to have MH by HBPM if the average was 135/85 mmHg or higher. Percentage agreements were quantified in terms of κ. We also examined the prevalence of MH, defined as office average less than 140/90 mmHg, with a 24-h ABPM average of 130/80 mmHg or higher. We carried out sensitivity analyses using different threshold BP levels for ABPM-office pairings and HBPM-office pairings for defining MH. RESULTS: Prevalence rates of MH based on office-awake ABPM pairings were 44 and 43%, with an agreement of 71% (κ=0.40; 95% confidence interval 0.31-0.49). MH was less prevalent (15 and 17%) using HBPM-office pairings, with agreement of 82% (κ=0.30; 95% confidence interval 0.16-0.44), and more prevalent when considering the 24-h average (50 and 48%). MH was also less prevalent when more stringent diagnostic criteria were applied. Office-HBPM pairings and office-awake ABPM pairings had fair agreement on MH classification on both occasions, with κ-values of 0.36 and 0.30. CONCLUSION: MH has fair short-term reproducibility, providing further evidence that for some people, out-of-office BP is systematically higher than that measured in the office setting.