LAURA ANN CLARK. Inpatient Resource Use and Cost Outcomes Among Kidney Transplant Recipients with vs. without Autosomal Dominant Polycystic Kidney Disease. (Under the direction of DR. REUBEN HOWDEN)Introduction: Autosomal dominant polycystic kidney disease (ADPKD) is a rare genetic condition impacting 1 in 400 live births in the United States (US) and it causes variable declines in kidney function to end-stage renal disease (ESRD). ADPKD accounts for approximately 5 to 10% of patients diagnosed with ESRD in the US and Europe. Between 50 and 70% of the ADPKD population require renal replacement therapy (RRT) (i.e., dialysis and kidney transplantation [KTP]) by their fourth to seventh decades of life, which exponentially increases the burden experienced by patients, caregivers, HCPs, and payers in the US. Patients with ADPKD, ESRD, and dialysis have been observed to have fewer 30-day unplanned hospital readmissions than patients without ADPKD, but the cost of index hospitalizations ($15,093 vs. $12,394) and 30-day all-cause readmissions ($17,391 vs. $16,455) was observed higher among those with ADPKD compared to those without ADPKD. Patients with ADPKD have been observed to have a higher rate of KTP within the first year of initiating dialysis compared to the total ESRD population in the US (25% vs. 5%, respectively). However, literature on the inpatient resource use and cost outcomes of patients with ADPKD and receiving KTP in the US is limited. This study aimed to leverage real-world data to generate estimates of inpatient resource use and cost of hospitalization for KTP surgery and 30-day all-cause readmissions among patients with vs. without ADPKD in the US.Methods: This study was a retrospective, longitudinal, case-cohort analysis of patients ≥18 years of age with an index hospitalization for KTP surgery between 01 January – 31 December 2018 in the Premier Healthcare Database (PHD). Patients with and without ADPKD were characterized at index hospitalization for KTP and 30-day all-cause readmissions within 30-days of index hospitalization for KTP surgery were identified between 01 January 2018 – 31 January 2019 in the PHD. Inpatient resource use (i.e., length of stay [LOS]) and total patient cost were compared for those with vs. without ADPKD at index hospitalization for KTP surgery. 30-day all-cause readmission outcomes (readmission rate, LOS, and total patient cost at readmission) were also compared for those with vs. without ADPKD. Descriptive (chi-square and Wilcoxon Signed-Rank Sum test) were applied for assessment of differences in outcomes at index hospitalization for KTP surgery and 30-day all-cause readmissions with alpha level set at ≤ 0.05. Inferential (logistic, negative binomial, and quantile regression) statistics were applied to assess the association between ADPKD diagnosis and 30-day all-cause readmission outcomes (i.e., readmission rate, LOS, total patient cost at readmission).Results: A total sample of 3,512 patients receiving KTP were obtained and stratified as ADPKD (n=285) and non-ADPKD (n=3,227) for comparison of patient demographics, Elixhauser comorbidities, hospital characteristics, inpatient resource use (i.e., LOS), and total patient cost at index hospitalization for KTP surgery. No significant difference was observed in the median (IQR) age of patients with vs. without ADPKD at index hospitalization for KTP surgery (56 [47-62] vs. 55 [43-63] years; p = 0.1658). However, a higher proportion of patients with ADPKD were aged 55-64 and 45-54 years old compared to patients without ADPKD (35% vs. 29% and 28% vs. 21%, respectively; p < 0.0001). A higher proportion of patients with ADPKD were female compared to those without ADPKD (46% vs. 38%, respectively; p = 0.0050). Patients without ADPKD were found to have a greater comorbidity presence and poorer health status with a higher proportion of patients without ADPKD having congestive heart failure (11% vs. 7%; p = 0.0498), valvular disease (5% vs. 3%; p = 0.0452), complicated hypertension (90% vs. 78%; p < 0.0001), complicated diabetes (45% vs. 9%; p < 0.0001), rheumatoid arthritis (7% vs. 1%; p < 0.0001), weight loss (4% vs. 1%; p = 0.0427), and alcohol abuse (2% vs. 0%; p = 0.0315) compared to those with ADPKD. However, a higher proportion of patients with ADPKD were identified to have uncomplicated hypertension compared to those without ADPKD (17% vs. 7%, respectively; p < 0.0001). The unadjusted median (IQR) LOS (4 [4-6] vs. 5 [4-7] days, respectively; p = 0.0006) and total patient cost ($103,000 [$72,000-$128,000] vs. $113,000 [$75,000-$139,000], respectively; p = 0.0010) at index hospitalization for KTP surgery were significantly lower among patients with ADPKD. A total of 1,582 patients (45.05%) of the total cohort were observed to have at least one all-cause readmission within 30-days of index discharge for KTP surgery. A lower proportion of patients with ADPKD (n=112) were observed have at least one all-cause readmission within 30-days of index discharge for KTP surgery compared to those without ADPKD (n=1,470) (39.30% vs. 45.55%, respectively; p = 0.0419). After adjustment for factors associated with the probability of ADPKD diagnosis, a 0.01% lower odds of at least one all-cause readmission within 30-days of index discharge for KTP surgery was observed, but it was no significant (OR: 0.99, 95% CI: 0.76 to 1.28, p = 0.9272). There was no significant difference in the unadjusted median (IQR) LOS (3 [2-6] vs. 3 [2-5] days, respectively; p = 0.4421) of 30-day all-cause readmissions among patients with ADPKD vs. without ADPKD. After adjustment for factors associated with the probability of ADPKD diagnosis, a 15% lower odds of a longer mean LOS at 30-day all-cause readmission was observed, but it was not significant (IRR: 0.85, 95% CI: 0.72 to 1.01, p = 0.0687). There was no significant difference in the unadjusted median (IQR) total patient cost ($8,575 [$4,904-$14,744] vs. $8,550 [$4,774-$16,940], respectively; p = 0.5364) of 30-day all-cause readmissions among patients with ADPKD vs. without ADPKD. After adjustment for factors associated with the probability of ADPKD diagnosis, a higher incremental median total patient cost was observed, but it was not significant ($1,252; 95% CI: -$1,057 to $3,088; p≥ 0.05).Conclusions: Patients with ADPKD and receiving KTP impose less inpatient resource use and cost burden to hospitals at index hospitalization for KTP surgery compared to those without ADPKD. Nearly half of patients included in this cohort experienced a 30-day all-cause readmission following KTP surgery, thus, there is a need for improvement in the quality of KTP care delivered across hospitals in the US. There was no association found between ADPKD diagnosis and the odds of at least one 30-day all-cause readmission. Furthermore, no association was found between ADPKD diagnosis and the burden imposed to hospitals (i.e., mean LOS and incremental median total patient cost) at 30-day all-cause readmissions. Lower comorbidity burden at index hospitalization for KTP surgery among patients with ADPKD likely impacted the readmission results. Ultimately, the economic burden to hospitals financially responsible for 30-day all-cause readmissions was determined equivalent for KTP patients with and without ADPKD in this study.