Assessment of different threshold preoperative glomerular filtration rates as markers of outcomes in lung transplantation

Abstract

Background: The evidence behind the widely used pre-lung transplant glomerular filtration rate (GFR) cutoff of 50 mL/min per 1.73 m2 is limited. This study reviews data from a large cohort to assess outcomes associated with this historical cutoff and to estimate other possible cutoffs that might be appropriate in lung transplantation.

Methods: We conducted a retrospective cohort analysis of lung recipients at a single center. Recursive partitioning and receiver operating characteristics analysis were used to estimate other potential GFR cutoffs with 1-year mortality as the outcome. Postoperative outcomes around the various cutoffs, including survival, acute kidney injury, and dialysis, were assessed using χ2, Kaplan-Meier, and Cox regression methods.

Results: A total of 794 lung recipients met study inclusion criteria. Compared with 778 patients with GFR 50 mL/min per 1.73 m2 or greater at time of transplant, 16 patients with GFR below this cutoff were older and more likely to have restrictive disease. One-year mortality below the cutoff was 31.3% compared with 15.1% above the cutoff (p=0.021). Recursive partitioning estimated potential GFR cutoff values between 46 and 61 mL/min per 1.73 m2. Patients with GFR below these cutoffs were at significantly higher risk for adverse outcomes (p<0.05). Receiver operating characteristics analysis was less successful at identifying meaningful cutoff values with areas under the curve approximately 0.5.

Conclusions: Study results support the practice of requiring candidate GFR 50 mL/min per 1.73 m2 or greater for lung transplantation. Future work should focus on reproducing the analysis in a larger cohort of patients including more individuals with low GFR.

Fig. 1

Kaplan-Meier analysis of survival to 2 years, stratified by GFR above or below specified cutoffs. (A) Cutoff, 50.0 mL/min per 1.73 m² (historical); (B) Cutoff, 48.0 mL/min per 1.73 m² (recursive); (C) Cutoff, 77.8 mL/min per 1.73 m² (receiver operating characteristic, ROC). We observed significant differences in mortality on either side of the historic and recursive partitioning cutoffs. The ROC established cutoff did not generate groups with differing mortality. (CI = confidence interval; HR = hazard ratio.)

Fig. 2

Receiver operating characteristics (ROC) curves displaying the sorting efficiency of Chronic Kidney Disease Epidemiology Collaboration glomerular filtration rate (GFR) for predicting post-lung transplant mortality at 1 year. The GFR value that maximizes the sum of sensitivity and specificity (ie, the ideal cutoff GFR values by the receiver operating characteristics method) is reported along with area under the curve (AUC). (CI = confidence interval.)