Survival of Primary and Repeat Lung Transplantation in the United States

Background This study was undertaken to compare survival between primary and repeat lung transplant recipients and to identify survival predictors after repeat lung transplantation. Methods Data for 10,846 primary and 354 repeat lung transplant patients were extracted from the United Network for Organ Sharing registry. Propensity score matching was used to examine balance in the distribution of potential observed confounders and to match the sample in terms of the probability of repeat lung transplantation given pretransplant characteristics alone. Matching based on the propensity score was used to compare survival between the primary and repeat lung transplant groups. A Cox regression model was used to identify risk factors for death in the cohort of patients receiving lung transplant. Results Considerable bias between the primary and repeat lung transplant groups was found in the sample. Patients with high propensity scores tended to carry high-risk profiles. Propensity score matching revealed incomplete overlap of covariate distributions between primary and repeat transplant groups. For those subjects who could be matched for the set of potential confounding variables, no difference in survival time was observed between primary and repeat lung transplant patients. Functional status and serum creatinine level were the two clinically important risk factors for predicting the survival of repeat transplant patients. Conclusions The current study revealed that direct comparison of the survival of primary and repeat lung transplant patients is biased by nonoverlap in the distribution of potential confounders. Using propensity score matching we adjusted for this bias and found that there was no significant difference in survival between first and second transplants.