Reproducibility of blood pressure response to hydrochlorothiazide. group vs. individual responses

Abstract

Few studies have investigated the reproducibility of responses to antihypertensive therapies. The purpose of this study was to assess the reproducibility of the blood pressure response to hydrochlorothiazide. Twenty-two subjects –11 non-Hispanic white adults from Rochester MN (5 women and 6 men) and 11 African-American adults (6 women and 5 men) from Atlanta GA– who underwent monotherapy with 25 mg of hydrochlorothiazide as part of a study to identify predictors of blood pressure response, agreed to undergo the same protocol a second time, 26.6 ± 11.8 (range: 4-52) months after their first participation. At the first study participation, the mean age of the 22 subjects was 49.0 ± 7.0 years, their mean body mass index was 31.3 ± 6.1 kg/m2, and their mean waist-to-hip ratio was 0.92 ± 0.08. At the second participation, means for body mass index and waist-to-hip ratio were not significantly different and individual values were highly correlated between the first and second participation (r = 0.96 and 0.95, respectively, P < 0.0001 for both). The mean systolic and diastolic blood responses (defined as the blood pressure before minus after treatment) to hydrochlorothiazide did not differ significantly between the first and second participation (systolic response: -14.2 ± l6.4 vs. -16.0 ± 16.5 mm Hg; diastolic response: -7.1 ± 11.8 vs. -6.6 ± 8.6 mm Hg), and these responses were significantly correlated between the two trials (systolic response: r = 0.61, P < 0.01 and diastolic response: r = 0.64, P < 0.01). However, both the direction and magnitude of responses for individual subjects varied considerably, with the limits of agreement between the first and second participations (i.e., 2 standard deviations above and below the mean difference between responses) ranging from 27.4 to -23.8 mm Hg for systolic blood pressure response and from 17.4 to -18.4 mm Hg for diastolic blood pressure response. These results show that the average systolic and diastolic blood pressure responses to hydrochlorothiazide for a group of subjects are reproducible; however, the responses for individual subjects are unpredictable.