title: Prediction of BOS by the single-breath nitrogen test in double lung transplant recipients.
abstract: BACKGROUND
  The present study analyses the ability of the alveolar slope of the single-breath nitrogen washout test (N2-slope) to diagnose and predict the development of the bronchiolitis obliterans syndrome (BOS).
  
  
  METHODS
  We present a retrospective analysis of 61 consecutive bilateral lung or heart-lung transplant recipients who were followed at regular control visits during a three year follow-up. The operating characteristics of the N2-slope to diagnose BOS and potential BOS (BOS 0-p) and to predict BOS were determined based on cut off values of 95% specificity.
  
  
  RESULTS
  The sensitivity of the N2-slope to identify BOS was 96%, and BOS 0-p 100%. The predictive ability to predict BOS with a N2-slope > 478% of the predicted normal was 56%, and if combined with a coincident FEV1 < 90% of the basal value, the predictive ability was 75%.
  
  
  CONCLUSIONS
  The predictive ability of either the N2-slope or of FEV1 to diagnose BOS is limited but the combination of the two appears useful. Follow-up protocols of bilateral lung and heart-lung transplant recipients should consider including tests sensitive to obstruction of the peripheral airways.
authors: Department of Respiratory Medicine and Allergology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. gerdt.riise@gu.se.
authors: Gerdt C
authors: GC
authors: Riise
authors: Gunnar
authors: G
authors: Mårtensson
authors: Birgitta
authors: B
authors: Houltz
authors: Björn
authors: B
authors: Bake