Objective: Evidence currently exist that treatment, and therefore prognosis, of the hypertensive patient can be improved by complementing the clinic blood pressure (BP) measurements with measurements taken out of the health care setting. The goal of the study was to validate a standard procedure of home BP self-measurement in contrast with a non invasive ambulatory BP monitoring (ABPM).
Method: This was a transversal and descriptive study set at the primary care level. 58 hypertensive patients with poor office control were instructed to self-measure their BP, with a previously verified digital sphygmomanometer, at home, 30 times for 10 days, and in the close 15 days an ABPM was taken for 24 hours. Reliability was determined comparing the degree of agreement between the different methods via the intraclass correlation coefficient (ICC) and the analysis of the individual differences.
Results: The self-measured BP and the ABPM do not differ significantly in systolic BP and only by 1.88 mmHg for the diastolic BP. The results taken in the office are significantly superior to those obtained by other methods -23 mmHg for the systolic BP and from 9 to 11 mmHg for the diastolic BP-. The ICC obtained comparing the results of the self-measured BP and ABPM are of 0.73 for systolic and 0.76 for the diastolic, whereas in the comparisons between office/self-measured, and office/ABPM the ICCs fluctuate from 0.23 to 0.50. The graphic analysis of individual differences allows the evaluation of the degree of reliability and the independence to the "white coat phenomenon".
Conclusions: The BP self-measurement protocol that we present is a valid instrument, capable of confirming hypertension as well a suspicion of "white coat phenomenon" particularly when the availability of ABPM is scarce.