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.