title: Use of the median for the evaluation of blood pressure self-measurement (BPSM).
abstract: 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 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.
  
  
  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.
authors.affiliation: Grupo Extremeño de Medicion De La Tensión Arterial, Badajoz, Spain.
authors.forename: Manuel Amaro
authors.initials: MA
authors.lastname: Lijarcio
authors.forename: Enrique Angulo
authors.initials: EA
authors.lastname: Yuste
authors.forename: Adolfo Arias
authors.initials: AA
authors.lastname: Senso
authors.forename: Javier Blanco
authors.initials: JB
authors.lastname: Aparicio
authors.forename: José Antonio de la Peña
authors.initials: JA
authors.lastname: Ruiz
authors.forename: Manuel Díez
authors.initials: MD
authors.lastname: García
authors.forename: Francisca Galindo
authors.initials: FG
authors.lastname: Tobal
authors.forename: Maria Luisa Martínez
authors.initials: ML
authors.lastname: Llarena
authors.forename: Candido Mena
authors.initials: CM
authors.lastname: Garcia
authors.forename: Francisco Parralejo
authors.initials: FP
authors.lastname: Cano
authors.forename: José F Pérez
authors.initials: JF
authors.lastname: Castán
authors.forename: Nicolas R Robles
authors.initials: NR
authors.lastname: Perez-Monteoliva
authors.forename: Natividad Sánchez
authors.initials: NS
authors.lastname: Santos