Accuracy of telemedical home blood pressure measurement in the diagnosis of hypertension.

This study was conducted to compare the accuracy of clinic blood pressure (CBP) and telemedical home blood pressure (HBP) measurement in the diagnosis of hypertension in primary care. The study subjects were 411 patients with average CBP > or =140 mmHg systolic or > or =90 mmHg diastolic, who performed telemedical HBP measurement (5 days, four times daily) and ambulatory blood pressure (ABP) monitoring in random order. Main outcome measure was the agreement of CBP and HBP with daytime ABP. CBP was much higher than daytime ABP and average HBP (P<0.001) with no difference between the latter two. The correlation between CBP and ABP was weak (systolic: r=0.499, diastolic: r=0.543), whereas strong correlations existed between HBP and ABP (systolic: r=0.847, diastolic: r=0.812). A progressive improvement in the strength of the linear regression between average HBP of single days and ABP was obtained from day 1 to day 4, with no further benefit obtained on the fifth day. The HBP readings taken at noon and in the afternoon showed significantly stronger correlations with ABP than the blood pressures measured in the morning and in the evening. In conclusion, the accuracy of telemedical HBP measurement was substantially better than that of CBP in the diagnosis of hypertension in primary care. HBP most accurately reflected ABP on the fourth day of monitoring, and the readings at noon and in the afternoon seemed to be most accurate.