title: Reproducibility of ambulatory blood pressure and assessing treatment withdrawal in hypertension trial.
abstract: Ambulatory blood pressure monitoring (ABPM), like casual blood pressure (BP), is imperfectly reproducible between visits. The reproducibility of ABPM is less than the reproducibility predicted from a simple model of random variation of BP. This suggests either increased technical error in the technique, an element of increased biologic variability, or both. In addition, ABP shows a between-day variation (add about 6 to 7 mm Hg diastolic, similar in magnitude to what is observed with casual BP) which cannot be obviated by the average of many within-day measurements. The reliability of ABPM, although conventionally judged excellent at about RI = 0.75, is insufficient to avoid misclassification errors and regression to the mean when BP cutpoints are employed. About 40% of patients apparently failing treatment withdrawal at a threshold of +2 SD, or about 95 mm Hg diastolic ABP, will be false-positive failures when categorized by a single ABP. Despite the inconvenience, obtaining an average of two or more ABP measurements on different days may be cost-saving to a clinical trial because of the improved reproducibility; other costs may exceed $1000 per entrant.
authors.affiliation: Department of Medicine, Sunnybrook Health Science Center, University of Toronto, Ontario, Canada.
authors.forename: R A
authors.initials: RA
authors.lastname: Reeves
authors.forename: M G
authors.initials: MG
authors.lastname: Myers
mesh_terms: D000553:Ambulatory Care; D001794:Blood Pressure / Q000502:physiology*; D015924:Blood Pressure Monitors; D002986:Clinical Trials as Topic; D006801:Humans; D006973:Hypertension / Q000188:drug therapy / Q000503:physiopathology*; D015203:Reproducibility of Results