Background: Bronchiolitis obliterans syndrome is defined by a >20% decrease from baseline in the forced expiratory volume in 1 second (FEV(1)). Recently, a consensus panel under the auspices of the International Society for Heart and Lung Transplantation proposed a new stage, designated "potential BOS" or BOS 0-p. This study sought to validate retrospectively this new stage in a cohort of single-lung transplant recipients.
Methods: A retrospective analysis of serial pulmonary function tests in 43 single-lung transplant recipients was performed. Baseline FEV(1) and midflow rate (FEF(25-75%)) were determined and compared with the most recent set of pulmonary function tests in clinically stable patients.
Results: The sensitivity of the FEF(25-75%) at <or=75% of baseline for subsequently detecting BOS Stage 1 was 80%, with a specificity of 82.6%. For the patients with idiopathic pulmonary fibrosis, the sensitivity was 62.5% and the specificity was 100.0%, whereas in the patients with chronic obstructive lung disease, the sensitivity was 91.7% and the specificity was 69.2%. Different cutoff points for the FEF(25-75%) also were tested and are shown in receiver operator curves. Likelihood ratios for the different cutoff points also were calculated. Five of 9 (55.6%) patients qualified for BOS 0-p using the FEV(1) parameter (FEV(1) of 81-90% of baseline) alone.
Conclusion: The FEF(25-75%) seems to be a useful criterion for predicting BOS development in single-lung transplant recipients. The FEF(25-75%) might best be used with likelihood ratios for different values rather than for 1 defined cutoff point of or=75% of baseline. The value of the second criterion that constitutes BOS 0-p (FEV(1), 81-90%of baseline) remains uncertain.