Prediction of BOS by the single-breath nitrogen test in double lung transplant recipients

BACKGROUND: The present study analyses the ability of the alveolar slope of the single-breath nitrogen washout test (N(2)-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 N(2)-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 N(2)-slope to identify BOS was 96%, and BOS 0-p 100%. The predictive ability to predict BOS with a N(2)-slope > 478% of the predicted normal was 56%, and if combined with a coincident FEV(1 )< 90% of the basal value, the predictive ability was 75%. CONCLUSIONS: The predictive ability of either the N(2)-slope or of FEV(1 )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.