Diffusing Capacity for Carbon Monoxide (DLCO): A Predictor of CLAD and Death after Lung Transplantation in a 20-Year Longitudinal Study

Abstract

Purpose The DLCO measures the capacity of the lungs to exchange gas across the alveolar-capillary interface. We hypothesized that DLCO is a sensitive measure of injurious allograft processes that can disrupt this interface. Our goals were to describe the trajectory of DLCO measurements after lung transplantation, and to determine the prognostic significance of DLCO on chronic lung allograft dysfunction (CLAD) and survival. Methods A retrospective cohort analysis was conducted of all bilateral lung transplant recipients at a single center, between Jan-1998 and Jan-2018, with ≥2 DLCO measurements. DLCO values were corrected for the nearest haemoglobin (DLCOcor). Low baseline DLCO was defined as the failure to ever attain a best achieved DLCO >75% predicted. Drops in DLCOcor were defined as >15% below best achieved. Multivariate Cox proportional hazard models were used for time-to-event analyses. Results 1158/1571 patients were included. The median (IQR) number of DLCOcor measurements per patient was 7 (5). The median (IQR) time to peak DLCOcor was 360 (555) days and the mean (SD) %-predicted DLCO was 81.2% (20.7). 433 patients (37.4%) had low baseline DLCO. Multivariate analysis demonstrated that low baseline DLCO was significantly associated with a shorter time to CLAD (HR 1.50 p Conclusion Low baseline DLCO was significantly associated with both CLAD and survival. Significant drops in DLCOcor at 18 months and the % predicted DLCO at CLAD onset were significantly and independently associated with reduced survival. There may be benefit in routine monitoring of DLCO after lung transplantation to identify patients at risk of poor outcomes.