Rationale: The association between a high predicted total lung capacity (pTLC) ratio (equal to pTLC(donor)/pTLC(recipient)), suggestive of an oversized allograft, with improved survival after lung transplantation (LTx) remains controversial.
Objectives: To characterize donor-recipient lung size matching based on the pTLC ratio and to investigate the relationship of the pTLC ratio with post-LTx survival.
Methods: All subjects in the Scientific Registry of Transplant Recipients, who underwent first-time LTx in the lung allocation score-based system between May 4, 2005 and March 31, 2012, were studied, and the pTLC ratio was calculated on the basis of sex, height, and age. Risk of death after LTx was analyzed using Cox proportional hazards models.
Measurements and main results: The pTLC ratio was available for 10,289 of the 10,318 study subjects (99.7%). The mean pTLC ratio was 1.015 ± 0.175 (interquartile range, 0.918-1.119). Univariate analysis showed that the pTLC ratio was strongly associated with death in the first LTx year (P < 0.0001). With the pTLC ratio entered as a spline there was a nonlinear association with declining risk of death with higher pTLC ratio from 0.5 to about 1.3, where an inflection occurred with rising risk at higher values. Accounting for the pTLC ratio, recipient and donor sex were not independently associated with death after LTx. A change of pTLC ratio from 0.918 to 1.119 (the interquartile range) was associated with similar point estimates of reduced risk of death at 1 year in univariate (hazard ratio, 0.78) and comprehensive risk-adjusted multivariate models (hazard ratio, 0.86).
Conclusions: The pTLC ratio is an independent predictor of death in the first year after LTx and explains the association of sex with survival after LTx. Incorporating the pTLC ratio in the lung allocation mechanism could improve outcomes after LTx.