Treated hypertension and the white coat phenomenon: Office readings are inadequate measures of efficacy.

To better define the prevalence of white coat hypertension (WCH) among patients with type 2 diabetes mellitus and to estimate the magnitude of white coat effect (WCE), before and after antihypertensive therapy, we gathered data from an open-label forced-titration study of a combination of antihypertensive drugs that was titrated sequentially, in the order amlodipine, olmesartan, and hydrochlorothiazide, over an 18-week period among 187 patients with type 2 diabetes mellitus. WCH was defined as daytime ambulatory blood pressure (BP) of 135/85 mm Hg or less, but clinic BP of 140/90 mm Hg or more. WCE was obtained as the mean difference between clinic and daytime ambulatory BP. At baseline, the prevalence of WCH was 12%; all but one subject had WCE of >10/5 mm Hg. After treatment, the prevalence of WCH had increased to 39% (P < .001). In the overall population, at baseline, the mean (±SD) WCE for systolic BP was 10.4 ± 10.9 mm Hg and 3.7 ± 8.6 mm Hg for diastolic BP. After treatment, the reduction in systolic WCE was 3.01 ± 0.93 (SE; P < .0001); no reduction was seen for diastolic WCE. Among patients treated with amlodipine-olmesartan combination, WCE at baseline was 11 mm Hg systolic and was attenuated to -0.9 mm Hg. Among patients treated with amlodipine-olmesartan-hydrochlorothiazide combination, systolic WCE was similar at baseline (10.1 mm Hg) and at end of therapy (8.1 mm Hg). Mean systolic difference between dual and triple therapy of 9.9 mm Hg, SE 2.98 was significant (P < .001). The drop in diastolic WCE from 6.4 with dual therapy to -1.2 with triple therapy was also significant (mean difference 7.6, SE 2.2; P < .001). In conclusion, the prevalence of WCH increases three-fold with treatment as a result of fewer patients having sustained hypertension. Thus, out-of-office BP monitoring especially among treated hypertensive patients with type 2 diabetes is necessary to provide better assessment of overall BP and response to treatment.