ObjectivesStandard operating procedures for office blood pressure measurement (OBPM) vary greatly between guidelines and studies. We aimed to compare the difference between a single OBPM and the mean of the three following measurements. Further, we studied how many patients with possible hypertension may be missed due to short-term masked hypertension (STMH) and how many might be overdiagnosed due to short-term white coat hypertension (STWCH).Design and settingIn this cross-sectional, single-centre trial, 1000 adult subjects were enrolled. After 5 min of rest, four sequential standard OBPMs were performed at 2 min intervals in a quiet room in sitting position. We compared the first (fBPM) to the mean of the second to fourth measurement (mBPM). STMH was defined as fBPM <140 mm Hg systolic and <90 mm Hg diastolic and mBPM systolic ≥140 mm Hg or diastolic ≥90 mm Hg. STWCH was defined as fBPM systolic ≥140 mm Hg or diastolic ≥90 mm Hg and mBPM <140 mm Hg systolic and <90 mm Hg diastolic.ResultsComplete measurements were available in 802 subjects. Between fBPM and mBPM, 662 (82.5%), 441 (55%) and 208 (25.9%) subjects showed a difference in systolic and 531 (66.2%), 247 (30.8%) and 51 (6.4%) in diastolic blood pressure (BP) values of >2 mm Hg, >5 mm Hg and >10 mm Hg, respectively. In 3.4% of initially normotensives STMH and in 34.3% of initially hypertensives, STWCH was apparent.ConclusionsThere are significant differences between a single OBPM and the mean of consecutive BP measurements. Our study provides evidence that a single OBPM should not be the preferred method and should be discouraged in future guidelines.Trial registration numberNCT02552030;Results.