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 (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.