Abstract
BackgroundThe 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).MethodsWe 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.ResultsThe 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%.ConclusionsThe 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.
Highlights
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)
Six months after transplantation the COuptake was substantially reduced and the N2-slope abnormally increased, but there were no significant differences between NoBOS and BOS patients
The present study shows that an abnormal N2-slope in combination with a FEV1 result < 90% of the basal value, predicts the development of BOS with a probability of 75%
Summary
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). Bronchiolitis obliterans is the leading cause limiting long-term survival after lung transplantation [1]. The prevalence is 50 to 60% in long-term survivors and account for 30% of all deaths after the third postoperative year [2]. During recent years new treatments have been attempted but the effect on long term survival has so far been limited [3,4]. A histologic diagnosis of bronchiolitis obliterans is usually not obtained due to the insensitivity of transbronchial biopsies [5]. The term bronchiolitis obliterans syndrome (BOS) was introduced and based on a ≥ 20% decrease in FEV1 rather than on histology [6]. BOS stage 0-p was put forward by Estenne et al in an update of the original staging system in order to identify
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