Ambulatory blood pressure monitoring in the evaluation of responses to antihypertensive therapy: advantages and difficulties

All published epidemiological data and major antihypertensive clinical trials as well as official guidelines for the diagnosis and management of hypertensive disease use clinical blood pressure measurements. However, clinical blood pressure measurement may not give the best estimate of the pharmacodynamics, the efficacy or the time-effect profile (the description of the effect of a given therapeutic agent throughout the interdosing interval) of antihypertensive agents. Clinical measurements provide blood pressure values for single time-points only, which, even using standardized measurement methods, are poorly reproducible and subject to 'white coat' and placebo effects. As a consequence, clinical trials as well as epidemiological studies relying on clinical blood pressure measurement need a substantial number of patients in order to attain sufficient statistical power. This increases dramatically the duration and cost of such studies. In addition, the time-effect profile, which is critical for deciding the size, the mode and the timing of drug dosing, requires repeated blood pressure measurements, ideally in a non-confined, ambulatory setting, which cannot be obtained with clinical blood pressure measurement Because ambulatory blood pressure can be measured automatically over 24 h (or more), in true ambulatory conditions, this method usually provides values that are more reproducible and less or not confounded by 'white coat' or placebo effects and which have better prognostic predicting value. As a result of these considerations, ambulatory blood pressure measurement may overcome some of the limitations of clinical blood pressure measurement as a tool for use in clinical trials and other longitudinal studies. I Hypertens 16 (suppl 9):S9-S13 (C) 1998 Lippincott Williams & Wilkins.