title: Reproducibility of the tolerance-hyperbaric test for diagnosing hypertension in pregnancy.
abstract: BACKGROUND
  The tolerance-hyperbaric test has been shown to provide a valuable approach for the prediction of the outcome of pregnancy. In this test, diagnosis of hypertension is based on the hyperbaric index (area of blood pressure excess above the upper limit of a reference threshold) calculated by comparison with a time-specified tolerance interval for the circadian variability of blood pressure.
  
  
  OBJECTIVE
  To evaluate prospectively the stability and reproducibility of the tolerance-hyperbaric test.
  
  
  METHODS
  We studied 403 women who provided 2430 blood pressure series sampled for 48 consecutive hours once every 4 weeks from the first obstetric visit (mostly within the first trimester of gestation) until delivery. Circadian 90% tolerance limits for blood pressure were established as a function of trimester of gestation from 497 series previously sampled from an independent reference group of 189 normotensive pregnant women. Diagnosis of hypertension was established in this trial for each woman in the validation sample on the highly restricted basis of presenting at least one blood pressure profile with a hyperbaric index above the threshold for diagnosis after 20 weeks of gestation.
  
  
  RESULTS
  Sensitivity of the tolerance-hyperbaric test was 93% for women sampled during the first trimester of gestation, and increased to 99% by the third trimester. Specificity was more than 99% in all trimesters. The positive and negative predictive values were greater than 96% in all trimesters.
  
  
  CONCLUSIONS
  The tolerance-hyperbaric test represents a reproducible, stable, non-invasive and high-sensitivity test for the very early identification of subsequent hypertension in pregnancy.
authors.affiliation: Bioengineering and Chronobiology Laboratories, University of Vigo, Campus Universitario, Vigo, 36200, Spain. rhermida@tsc.uvigo.es
authors.forename: Ramón C
authors.initials: RC
authors.lastname: Hermida
authors.forename: Diana E
authors.initials: DE
authors.lastname: Ayala
authors.forename: José R
authors.initials: JR
authors.lastname: Fernández
authors.forename: Artemio
authors.initials: A
authors.lastname: Mojón
authors.forename: Manuel
authors.initials: M
authors.lastname: Iglesias
mesh_terms: D000328:Adult; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods / Q000592:standards*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000175:diagnosis*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity