How many self-measured blood pressure readings are needed to estimate hypertensive patients' "true" blood pressure?

The present research was aimed at determining the number of self-measured blood pressure (BP) readings needed to attain reliable estimates of true BP in hypertensive patients. Correlation coefficients and standard deviation of differences between pairs of measurements as well as generalizability theory were applied to data from a controlled study on stress management training for essential hypertension (Garcia-Vera et al., 1997). Forty-three hypertensive patients self-recorded 48 readings of BP (at home and at work) at both the pretreatment and the posttreatment (separated by a period of 2 months) and 24 readings of BP at follow-lip (6 months after the pretreatment). The results showed that it is enough to take two readings, one at work and the other at home, from each of 3 consecutive days to get reliable estimates of SEP and DBP across settings, over I week and over 2 months. This same criterion would be valid to get reliable estimates of DBP over 6 months, but two readings, one at work and the other at home, from 8 or more consecutive days may need to be taken to achieve similarly reliable results for SBP.