Between 5/2005 and 6/2009, 84 patients received LTx at our institution. The mean age was 49±13years with 47% females (n=40). Recipient race distribution was:81% Caucasian (n=68), 17% African American (n=14), and 2% Hispanic (n=2). Diagnoses were: Chronic obstructive pulmonary disease (COPD) in 25 (29.7%), idiopathic pulmonary fibrosis (IPF) in 18 (21.4%), cystic fibrosis (CF) in 16 (19.0%), primary pulmonary hypertension in 4 (4.7%), bronchiolitis obliterans syndrome in 6 (7.1%), sarcoidosis in 5 (6.0%), and other in 10 (11.9%) of patients. 73 (87%) patients received bilateral LTx (BLTx). 19 (23%) patients’ required ICU care pre-LTx. The majority of patients (67%) received induction immunotherapy with daclizumab (Zenapax, Hoffmann-LaRoche Inc, Nutley, NJ). Median wait-list time was 70 (IQR:19–527) days. During the study, the number of adult LTx’s remained constant, ranging from 14–21 LTx’s annually.
Mean LAS for the entire cohort was 42.5 (±14.4). LAS quartiles were: Q1, 30.1–34.3, n=21; Q2, 34.4–37.5, n=21; Q3, 37.6–44.8, n=21; Q4, 44.9–94.3, n=21. Baseline demographic information was compared between Q1–3 and Q4 (). Patients in Q4 had shorter wait-list times and were more likely to require pre-LTx ICU care, have diabetes mellitus, and had higher oxygen requirements. Predicted forced expiratory volume in 1 second (FEV1) was lower in Q1–3. Ischemia time was similar in both groups, as were all examined donor characteristics.
Outcomes and Survival
Mean follow-up was 19±14months. Re-admission rates between Q4 and Q1–3 were similar. Q4 patients had longer median hospital and ICU LOS; patients in Q4 also had longer duration of mechanical ventilation, more re-intubations, and greater need for tracheostomy. No difference was seen for RRT, in-hospital infections, or in-hospital mortality ().
Postoperative Outcomes According to LAS Group
During the study, 27 (32.1%) patients died and 17 (20.2%) patients did not survive one year. When the cohort was analyzed without stratification, overall 1-year survival was 76.2%. After stratification by Q1–3 versus Q4 there was no difference in 30-day, 90-day, or 1-year KM survival. However, there was a trend toward improved survival in Q1–3 (). Further division into individual LAS quartiles revealed no significant survival differences, however a trend toward improved 1-year survival was evident for Q1 patients (90.2% versus 71.4% for Q4) ().
Kaplan Meier Estimates of 1-Year Survival Stratified by LAS Q1–3 Versus LAS Q4. By Log-Rank analysis, survival was similar between the two groups.
Kaplan Meier Estimates of 1-Year Survival Stratified by Individual Quartiles. By Log-Rank analysis, survival was improved in Q1 patients (90% 1-yr survival) compared to the remaining three quartiles (p<0.05).
Median index admission charges were higher in LAS Q4 patients: $276,668 (IQR191,301–300,156) for Q4 compared with $153,995 (IQR129,796–176,849) for Q1–3, p<0.001 (). Median index admission charges for individual quartiles are listed in ). Total median 1-year hospital charges were greater in Q4 patients: $316,213 (IQR: 245,794–469,006 for Q4 versus $190,261 (IQR: 153,455–240,364) for Q1–3, p=0.002. After excluding index admission charges, there was no difference in median 1-year hospital charges between the two groups: $44,657 (IQR: 9,041–123,369) for Q4 compared to $27,875 (IQR: 13,831–7,160), p=0.3. Among patients who died within one year, there was no difference in total charges when comparing Q4 to Q1–3. When examining individual LAS quartiles, Q4 patients had significantly higher index admission charges compared with all other quartiles. There were no differences among Q1, Q2, or Q3 when analyzing index admission charges.
Figure 3 Breakdown of Median Charges According to LAS Quartile. Rank-sum comparison showed index admission and total 1-year charges were higher for LAS Q4 patients compared with LAS Q1–3 patients (p=0.004 for Index Admission and p=0.008 for Total 1-year (more ...)
Median Charges Values According to LAS Quartile
For LAS Q4 and Q1–3, the relative contributions of each charge category to total index hospitalization charges are depicted in and . Hospital charges according to category were compared between LAS Q4 and Q1–3. When analyzing index admission charges only, the following categories were higher for LAS Q4: OR supplies charges, OR facilities charges, routine ward and ICU care, pharmacy charges, and laboratory services. There was no difference in radiology or physical therapy services.
Pie Chart Depicting Charges by Category for LAS Q1–3
Pie Chart Depicting Charges by Category for LAS Q4
Area under the ROC curve was 0.76 (95% CI: 0.64–0.89) (). An LAS of 43.314 had the best discriminatory power for predicting the upper 25% of index admission charges, with sensitivity of 67% and specificity 84%. Adjusting the LAS threshold to 45.2 achieved a specificity of 88% but decreased sensitivity to 54%.
ROC Curve for Increased Index Admission Charges (Upper 25% of Index Admission Charges). Area under the curve was 0.76 (95% CI:0.64–0.89). An LAS of 45.2 had 88% specificity and 54% sensitivity for predicting outcome of interest.
Linear Regression Analysis
Linear regression of charges data after logarithmic transformation revealed a positive correlation between LAS and index admission charges (coefficient: 0.009, 95%CI 0.001–0.017, p=0.03), with a Spearman r-value of 0.28 (). Similarly, there was a positive correlation between LAS and 1-year charges including index admission (coefficient: 0.010, 95%CI 0.001–0.020, p=0.04), with a Spearman r-value of 0.23. Following adjustment with multivariable linear regression, ICU pre-LTx (coefficient: 0.22, 95% CI 0.001–0.44, p=0.05), duration of mechanical ventilation postoperatively (0.004, 95% CI 0.002–0.005, p<0.001), RRT (0.41, 95% CI 0.11–0.69, p<0.006), and tracheostomy (0.61, 95% CI 0.36–0.84, p<0.001) were significantly associated with index admission charges ().
Scatter Plot of Log Linear Index Admission Charges According to LAS. There was a significant positive correlation (0.009, p=0.03), however weak goodness of fit for the linear model with spearman’s R-value=0.28.
Results of Linear Regression Analysis