Use of the median for the evaluation of blood pressure self-measurement (BPSM)

Background: One of the disadvantages of blood pressure self-measurement (BPSM) is that it requires doctors to carry out cumbersome calculations involving a large number of figures during the medical visit. Here, we compare the use of median blood pressure values to mean blood pressure values as a diagnostic criterion for home BPSM. Methods: Self-measurements from 253 patients (51.1 +/- 12.2 years, 48% male and 52% female) were collected. Sixty-two percent of these patients were receiving antihypertensive treatment. Each patient was given an OMROM 705 monitor to carry out the blood pressure measurements at home. A total of 12 measurements were taken, 2 in the morning and 2 in the afternoon for 3 consecutive days. The mean and median values were calculated for each patient. Results: The median SBP (143.04 +/- 18.53 mmHg) did not differ from the mean SBP (143.1 +/- 18.85 mmHg). The same was true for DBP (median 82.25 +/- 9.56; mean 82.26 +/- 9.39 mmHg). There were no significant differences in the classification of the patients with regard to whether the median or the mean was used. Some 47.3% of the measurements bad a mean SBP below 135 and 79.8% had a mean DBP below 85 mmHg. Using the median, SBP was below 135 in 48.4% of the cases and DBP below 85 in 82.01% of the cases. Differences were not significant. The sensitivity of the median for SBP was 97.0% and the specificity was 97.0%. False-positives were 1.60% and false-negatives 1.18%. The sensitivity of the median for DBP was 94.0% and the specificity was 97.0%. False-positives were 1.18% and false-negatives 3.95%. The kappa coefficient was 0.994 for SBP and 0.882 for DBP. Conclusions: The median seems to be a valid alternative to the mean in the evaluation of BPSN results, offering good sensitivity and specificity and greater ease of use in daily practice. (C) 2006 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.