Home Self Blood Pressure Measurement in General Practice The SMART Study

The SMART study (Self-Measurement for the Assessment of the Response to Trandolapril) was performed in general practice and enrolled 1710 patients in order to assess on a large scale the feasibility and informative value of self-measurement of blood pressure at home (SMBP), define home blood pressure (BP) levels in comparison to office readings, and determine the number of home measurements necessary to provide an accurate and precise BP value. After a 2-week washout period, patients with office diastolic blood pressure within the range 95 to 119 mm Hg received 2 mg trandolapril once daily in the morning for 4 weeks. Four days of SMBP were performed both at the end of the washout period and the end of the treatment period, with an automatic printer-equipped oscillometric device (A&D UA751). The first day values were not analyzed. Thus, the maximum number of BP measurements obtained per patient and per period was 18. Four hundred and twenty-four patients (25%) did not perform any measurements. One thousand one hundred and nine patients (65%) performed at least 4 measurements. Among them, 619 (36%) correctly performed all 18 measurements. A preference for digits 0 and 5 was detected in physicians' measurements (three consecutive values, during a single office visit). This digit preference was not found with the semiautomatic device. When the number of measurements selected for analysis was increased from 1 to 18, in the 604 patients who provided all recordings and fullfilled all protocol criteria, the standard deviation of the mean BP of the cohort was reduced by 17% for SBP and by 23% for DBP. Eighty-five percent of this reduction was already achieved by six home measurements taken at random. BP was significantly lower at home than at the office by 13 +/- 15 mm Hg for systolic BP (SBP), and 8 +/- 10 mm Hg for diastolic BP (DBP). This difference was independent of age, more marked in women (P < .001 for SBP and P < .05 for DBP), and had a Gaussian distribution. Under treatment, office SBP/DBP decreased from 166.4 +/- 14.8/101.4 +/- 5.7 mm Hg to 144.7 +/- 14.2/86.1 +/- 8.3 mm Hg, while SMBP decreased from 153.2 +/- 17.8/93.8 +/- 10.1 mm Hg to 139.4 +/- 16.4/85.1 +/- 9.5 mm Hg (all P < .0001). A major aim in research studies and individual care is to reduce BP measurements variability. This study demonstrates the ability to evaluate baseline SMBP level in two-thirds of patients previously unfamiliar with the method, the ability to evaluate treatment effect in about one-half of the patients, the improvement in the measurement precision obtained with the repetition of measures (at least six home measurements), and the absence of bias of SMBP as compared to office measurements.