[Influence of protocol on the quality of blood pressure self-monitoring]

To determine the minimum number of self-measurements of blood pressure to provide the maximum quality and reliability during home-blood pressure monitoring.

We studied 38 hypertensive subjects in which we compared self-reported with electronically stored home BP (OMRON HEM 720 CIC). Subjects were asked to measure BP in the sitting position, three times consecutively in the morning and three times in the evening during 7 consecutive days. BP values over the 7 days were averaged and the differences with BP recorded over the first day (6 values per day), the first 2 days, the first 3 days, the first 4 days, the first 5 days and the first 6 days were calculated. Confidence interval were calculated.

We observed that 47% of patients completed the entire protocol (42 measurements over 7 days), but 89% completed 4 days with 6 measurements. Erroneous reporting was evident in 10% of patients. In patients which performed 100% of the 42 planned values, confidence interval for the mean value was < 4 mmHg for SBP and < 3 mmHg for DBP when the patient completed a 4 days protocol with a minimum of 4 measurements per day.

These results indicate that determining average home blood pressure over 4 consecutive days with 2 measurements twice daily, is the minimum protocol that provides a reliable estimate of home blood pressure with a good quality of patient reporting.