Prevalence of masked hypertension in attended versus unattended office blood pressure measurement.

Abstract

There is a controversial debate regarding whether unattended blood pressure (BP) measurement should be regarded as the new gold standard of office BP measurement. Unattended BP measurement eliminates the white-coat effect and reduces external influences on the patient. On the other hand, it might underestimate real-life BP. The present study compares the prevalence of masked hypertension using attended versus unattended office BP measurements. We performed a cross-sectional study on 213 patients in a general practitioner's outpatient clinic and compared attended and unattended office BP with 24h-ambulatory BP monitoring (24h-ABPM). Masked hypertension was defined as pressure ≥135/85mmHg in daytime ABPM with office systolic BP<140/90mmHg. Median attended and unattended office BPs were 140/86 and 134/80mmHg with a median 24h-BP of 129/79mmHg and daytime ABP of 133/82mmHg. The number of patients with masked hypertension was 45/213 (21.2%) using unattended and 23/213 (10.8%) using attended office BP measurements (p<.0001). Bland-Altman analysis revealed a 7.4mmHg systolic and 6.2mmHg diastolic bias between the attended versus unattended office BP, and two systolic and -1.7mmHg diastolic biases between the unattended office BP and daytime ambulatory BP. In linear regression analysis, an unattended office BP of 134mmHg corresponded to 140mmHg in attended BP measurement. Using a cut-off of 135/85mmHg instead of 140/90mmHg in unattended office BP measurement, the rate of masked hypertension was 26/213 (12.2%). Thus, unattended office BP measurement results in a substantial increase in the prevalence of masked hypertension using the traditional definition of hypertension. The present findings suggest that it might be reasonable to use a definition of 135/85mmHg.