Abstract
BACKGROUND: Masked hypertension (MH)--nonelevated office blood pressure (BP) with elevated out-of-office BP average--conveys cardiovascular risk similar to or approaching sustained hypertension, making its detection of potential clinical importance. However, it may not be feasible or cost-effective to perform ambulatory BP monitoring (ABPM) on all patients with a nonelevated office BP. There likely exists a level of office BP below which ABPM is not warranted because the probability of MH is low. METHODS: We analyzed data from 294 adults aged ≥ 30 years not on BP-lowering medication with office BP <140/90 mm Hg, all of whom underwent 24-hour ABPM. We calculated sensitivity, false-positive rate, and likelihood ratios (LRs) for the range of office BP cutoffs from 110 to 138 mm Hg systolic and from 68 to 88 mm Hg diastolic for detecting MH. RESULTS: The systolic BP cutoff with the highest +LR for detecting MH (1.8) was 120 mm Hg, and the diastolic cutoff with the highest +LR (2.4) was 82 mm Hg. However, the systolic level of 120 mm Hg had a false-positive rate of 42%, and the diastolic level of 82 mm Hg had a sensitivity of only 39%. CONCLUSIONS: The cutoff of office BP with the best overall operating characteristics for diagnosing MH is approximately 120/82 mm Hg. However, this cutoff may have an unacceptably high false-positive rate. Clinical risk tools to identify patients with nonelevated office BP for whom ABPM should be considered will likely need to include factors in addition to office BP.