Reproducibility of 24-hour non-invasive ambulatory blood pressure monitoring using the Suntech Accutracker.

1. The reproducibility of 24-hour non-invasive ambulatory blood pressure monitoring (ABPM) using the 'Accutracker' (AC) (Suntech Medical Instruments, NC) was determined to evaluate the AC's suitability for clinical trials investigating the effects of environmental determinants on blood pressure. 2. Six healthy males from the University Department of Medicine underwent 24 h ABPM on the same working day of the week on six occasions. Reproducibility of hourly mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) was determined using analysis of variance. 3. No familiarization effect of measurement with the AC was detected. 4. When comparing four time periods (0000-0759 h, 0800-1259 h, 1300-1859 h and 1900-2359 h), reproducibility of SBP was highest during the afternoon (1300-1859 h) whereas reproducibility of DBP was highest during late morning (0800-1259 h). 5. Hourly mean SBP was significantly lower during late morning (0800-1259 h) than in the afternoon (1300-1859 h) or at night (1900-2359 h). Hourly mean SBP and DBP was significantly lower during sleep. 6. Based on a select sample of volunteers, the AC is suitable for clinical trials involving paired measurements, particularly between 0800 and 1900 h when only 10-15 subjects would provide 80% power to demonstrate a 5 mmHg difference in SBP and DBP significant at the 0.05 level.