Office blood pressure and 24-hour ambulatory blood pressure measurements: high proportion of disagreement in resistant hypertension.

Objective: To evaluate the accuracy and quantify the agreement between office blood pressure (BP) and daytime ambulatory BP monitoring in the assessment of BP control of patients with a clinical diagnosis of resistant hypertension.

Study Design And Setting: Office BP measurements were done in a cohort of 228 true resistant (TR) or white-coat resistant (WCR) hypertensives classified by ambulatory BP in a hypertension clinic in Rio de Janeiro in this validity study. The agreement between the daytime ambulatory BP and office BP was analyzed using the graphic methods of Altman -- Bland and survival -- agreement plots.

Results: The likelihood ratio of a positive test result of office BP was 1.99 for the assessment of uncontrolled BP in TR patients and 1.05 for the WCR hypertensive patients. The Altman and Bland plot showed a significant difference between the two methods, and the presence of a fixed and a proportional bias. The survival-agreement plot showed that a tolerance limit of 20 mm Hg of difference between systolic office BP and systolic daytime ambulatory BP would generate a proportion of disagreement equal to 57.5%.

Conclusion: The office BP is still an important tool to monitor BP control of patients with TR hypertension, whereas the monitoring of patients with WCR hypertension requires ambulatory BP.