LONG-TERM REPRODUCIBILITY, OF AMBULATORY BLOOD-PRESSURE

Objective: To compare the reproducibility of ambulatory and office blo od pressure readings in established hypertensive subjects when studies are repeated at extended time intervals. Subjects: Twenty-five hypert ensive patients (office diastolic blood pressure greater than or equal to 90 mmHg) who were off antihypertensive therapy for at least 4 week s and had repeat office and ambulatory blood pressures at least 3 mont hs apart under similar study conditions. Methods: On the same day, pat ients underwent office blood pressure readings measured by mercury col umn sphygmomanometry and then by ambulatory blood pressure monitoring. Ambulatory blood pressure monitoring was done for 24 h, and awake and sleep periods were divided according to a diary kept by each patient. A second study was performed in an identical manner at a mean +/- SD interval of 23 +/- 24 months (range 3-80, median 15). The agreement be tween studies was assessed by correlation coefficients, coefficients o f variation and standard deviation of the differences (SDD). Results: There were no significant differences in office, 24-h, awake and sleep mean blood pressures between the two studies. Mean 24-h systolic and diastolic blood pressures were 16 and 14 mmHg lower, respectively, tha n office blood pressure values. Correlation coefficients were signific antly higher for 24-h ambulatory blood pressure than office blood pres sure, whereas the SDD between visits was significantly lower for 24-h ambulatory blood pressure than office blood pressure. Conclusions: The se data demonstrate that long-term reproducibility of ambulatory blood pressure is superior to that for office measurement. One implication of this finding is that, in long-term clinical pharmacology trials uti lizing ambulatory blood pressure, fewer subjects would be required tha n for studies that used office blood pressure end-points.