Home-based self-measurement of blood pressure: a proposal using new reference values (the PURAS study).

OBJECTIVES: To establish reference values for blood pressure by means of self-measurement of blood pressure (BP) conducted at home.

DESIGN: Descriptive study of the distribution of self-measured BP at home and its correspondence with clinic-based measurements of BP.

METHODS: The aim of this study is to define the home BP levels that correspond to clinic BP thresholds 140/90 mmHg (hypertension) and 130/85 mmHg (normality). The sample consisting of 1411 randomly selected adults stratified by age and gender. A pre-calibrated electronic device (Omron 705CP) was used for BP and heart rate (HR) measurements and a trained nurse performed clinic-based sphygmomanometer measurements. The same nurse provided tutorials for the subjects on how to obtain 12 self-measured BP values at home using the Omron device in a single day.

RESULTS: Of the 1184 volunteers that attended the appointment, 195 were known as hypertensives and were excluded from the study. The average age of the remaining 989 subjects (50.4% females) was 44.3 years. Clinic BP values were significantly higher than self-measured BP at home regardless of age and gender. Both had good correlations (systolic BP, r=0.84 and diastolic BP, r=0.77). Using linear regression, the self-measured BP at home hypertension threshold would be 131/82 mmHg and the limit of normality 123/78 mmHg. Using corresponding percentiles, these values would be 134/85 and 124/80 mmHg, respectively.

CONCLUSIONS: The self-measured BP at home values found in this study, when defining hypertension, are lower than values currently accepted (135/85 mmHg). Long-term studies are necessary to confirm these results.