Impact of serial lung function metrics after lung transplantation: a retrospective cohort study

<bold>Background:</bold> Despite significant progress in recent years, the mortality rate following double lung transplantation (DLTx) remain higher than those observed for other solid organ transplantations. Traditionally, serial longitudinal monitoring has relied on dynamic spirometric indices, but diffusing capacity of the lung for carbon monoxide corrected for hemoglobin (DLCOc) is now also routinely assessed. Here, we sought to investigate the relative impact of changes in FEV1, FVC, and DLCOc from serial testing over time on all-cause mortality after DLTx. <bold>Methods:</bold> We conducted a retrospective cohort study and included a total of 234 patients who underwent DLTx at a tertiary hospital between January 2012 and January 2019. We performed a time-dependent multivariable Cox hazards model, including all available lung function tests after transplantation. It was performed to evaluate the association between baseline characteristics, sex, native lung disease and changes in lung function metrics over time with all-cause mortality from transplant to death, re-transplantation or to end of follow-up. <bold>Results:</bold> Following time-dependent multivariable analysis adjusted for predictors of mortality, FEV1 (HR 1.01, 95% CI: 1.004-1.017, p = 0.002), FVC (HR 1.011 95% CI: 1.001-1.021, p = 0.025) and DLCOc (HR 1.016 95% CI: 1.005-1.028, p = 0.006) as % of predicted all remained significantly associated with all-cause mortality. <bold>Conclusion:</bold> Both reduced FEV1, FVC and DLCOc as % of predicted are independent predictors of death in DLTx patients over time regardless of baseline characteristics, supporting the clinical use of serial full lung function testing for risk assessment and prognostic stratification.