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

BackgroundOne 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.MethodsSelf-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.ResultsThe 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 had 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.ConclusionsThe 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.