Ambulatory blood pressure measurement: therapeutic implications.

Conventional clinic measurement of blood pressure has many deficiencies, among which the most significant are its inability to indicate the duration of drug effect, or the influence of antihypertensive drugs on nocturnal blood pressure. The technique is, therefore, unreliable for assessing antihypertensive drug efficacy, either in clinical practice or hypertension research. Non-invasive 24 h ambulatory blood pressure measurement has a number of advantages over conventional measurement. In clinical practice it provides a profile of blood pressure over the 24 h period permitting the selection of the most appropriate antihypertensive drug for the individual patient. In studies of antihypertensive drug effect, ambulatory measurement detects white coat responders and, being free of regression to the mean and the placebo response, it is possible to consider efficacy studies which need not have a placebo phase. By providing considerably more observations than can be obtained with clinic measurement, ambulatory measurement increases the power of studies making it likely that fewer numbers of patients are needed for antihypertensive drug studies. 24 h ambulatory blood pressure measurement offers the opportunity to study antihypertensive drugs in fewer patients with greater accuracy than is possible with conventional clinic measurement and should be a mandatory requirement for such studies.