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SDC, Materials and Methods
National Data Methods
National data included adult single or bilateral lung transplant recipients between May 1, 2005 and December 31, 2014 supplied (as of March 13, 2015) by the United Network for Organ Sharing (UNOS) as the contractor for the Organ Procurement and Transplantation Network (OPTN). Interpretation and reporting of these data were the responsibility of the authors and not an official policy or an interpretation by the OPTN or the U.S. Government. For analysis of LOS comparing UNOS and Mayo data we utilized the UNOS reported LOS definition, which extends from the day of transplant to the day of discharge of that transplant episode including dismissal to home, transfer to another acute care hospital or a rehabilitation facility.
Statistical analysis
Mayo Data
Descriptive statistics included means and standard deviations, or medians and selected percentiles for skewed distributions. Statistical assessments were based on Chi-square tests for discrete variables, Kruskal Wallis rank-sum tests for continuous variables and log-rank tests for graft and patient survival. Regression models
examining the relationships of LAS and waiting time used a log transformation for waiting time and the model of LAS and cost used a log transformation for cost. The relationship of LAS and posttransplant survival was based on a logistic regression model. All regression models included both LAS and calendar year as independent variables to adjust for potential changes in standardized costs not due to inflation. An interaction term between LAS and calendar year was added to each model to see if
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the relationship between LAS and that outcome significantly changed over time. Cost models also included patient age, sex, and type of transplant (bilateral vs. single). All analyses were performed with SAS version 9.4 (Cary, NC).
Secondary analysis was carried out to assess the potential impact of posttransplant mortality on posttransplant costs. Mean posttransplant costs per month of follow-up were compared across the LAS groups with a Kruskal Wallis rank-sum test.
National Data
Statistical assessments comparing Mayo Clinic experience to US experience were based on Chi-square tests for discrete variables and Kruskal Wallis tests for
continuous variables.
National Data Results
Overall, Mayo Clinic patients were of older mean age (p<0.001), had increased number of single lung transplants (p=0.026), and shorter overall LOS (p<0.001) than the national cohort (Table 1). Survival at 1, 2, and 5 years posttransplant were not significantly different between groups. Higher percent of Mayo Clinic patients had diagnosis of restrictive lung disease (p<0.001) and lower percent had bronchiectasis (p<0.001) and obstructive lung disease (p=0.013). Mayo patients had higher LAS at the time of the transplant (mean+sd: 51.3 +19.9 vs. 47.0 +17.4; median: 43.6 vs.
40.3; p<0.001) but not at listing (p=0.242), and Mayo Clinic had a greater percentage of patients transplanted with LAS score >80 (16.3% vs. 9.6%, p<0.001).
At the national level, the mean LAS at listing has increased from 38.3 in 2005 to 44.9 in 2014, while LAS at transplant rose by 11.5 points from 40.6 in 2005 to 52.1 by 2014 with median rising from 36.6 in 2005 to 44.7 in 2014 (Figure S1). Despite rising LAS, the overall posttransplant survival has significantly increased nationally (Figure
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S2). Overall, 835 (5.3%) UNOS patients receiving lung transplant died prior to discharge. The national 1-year patient survival has risen from 82.6% in 2005 to 87.2% in 2013 (p<0.0001). Two-year survival rose from 74.1% in 2005 to 78.5% in 2012 (p<0.0001). Five-year survival remained consistent nationally (54.4% in 2005, 56.3% in 2009; p=0.058).
Despite the overall increase in more recent years in survival, higher LAS was
negatively associated with lower posttransplant survival in the UNOS data (Table 2).
Survival rates at 1, 2, and 5 years for patients transplanted with LAS 60-79 were 81.7%, 71.1%, and 48.2% and for LAS >80 were 76.6%, 65.3%, and 46.7%,
respectively, compared to 86.6%, 77.5%, and 56.0% for LAS <40 (p<0.001). LAS at transplant was dramatically higher for hospitalized and ICU patients compared to outpatients in both the Mayo Clinic and UNOS data. For UNOS and Mayo Clinic groups, the mean LAS score at transplant for nonhospitalized patients were 42.2 + 11.6 and 43.0 + 10.9, respectively, while it was 75.2 + 20.9 and 82.0 + 14.6 for ICU patients (p<0.001). Similar differences were seen in quartiles.
4 Figure S1
5 Figure S2
