In previous studies we found that the increase in blood pressure (BP) induced by clinical measurement, the so called white coat effect (WCE), is frequently observed also during ambulatory blood pressure monitoring (ABPM). As in these hyperreactive patients performing a full 24-hours examination can be cumbersome, we examined to what extent the mean values of systolic BP collected at the third hour (3hSBP), when WCE tends to wear off, are representative of the mean diurnal systolic BP values (mDSBP).Design and method:
In 429 ABPM (M/F 144/285) in which WCE was detected when the first systolic recorded value was at least 10 mmHg higher than mDSBP, we compared 3hSBP and mDSBP assuming a mean value of 135 mmHg as the upper limit of normotension.Results:
As expected considering all ABPM there was a progressive decrease of mean values from the first to the third hour of recording (respectively 153, 139 and 134 mmHg) whereas mDSBP was 135 mmHg. Out of the 429 ABPM, 190 (44%) were above this limit with 3hSBP and 206 (48%) for mDSBP. However only 147 (34%) and 180 (42%) were diagnosed respectively as hypertensive or normotensive with both measurements, whereas 43 (10%) of those found hypertensive with 3hSBP were not so with mDSBP and 59 (14%) normotensive with 3hSBP were diagnosed as hypertensive with mDSBP. Thus inspite of the fact that overall there was a significant correlation between 3hSBP and mDSBP (r = 0.72; p < 0.01), 102 (24%) patients had a discordant diagnosis.Conclusions:
Although 3hSBP provides some insight on DSBP in patients with WCE, the percent of incorrect diagnoses with 3hSBP is too high to justify the use of 3hSBP as a surrogate of conventional DSBP.