THE IMPACT OF AUTOMATED BLOOD-PRESSURE DEVICES ON THE EFFICIENCY OF CLINICAL-TRIALS

By reducing measurement error, automated blood pressure (BP) devices should enhance the precision of BP estimation and thereby decrease sample size requirements in clinical trials of BP-lowering therapy. Enhanced precision would be particularly relevant to clinical trials assessing the efficacy of nonpharmacological therapies. In the present investigation, resting (clinic) BPs by the Dinamap 8100 (a stationary device) and the Accutracker II (an ambulatory device) were as precise as manual BPs given an equal number of observations by each method. However, both the Dinamap and Accutracker devices underestimated resting diastolic BP in comparison to the manual observers. Estimates of average daytime and 24-hour ambulatory BP, based on large numbers of observations over an extended period of time, were extremely precise. These findings suggest that the use of automated devices to measure resting BP may not reduce samples sizes, whereas use of ambulatory BP devices should reduce samples sizes considerably.