Dialysis Case Volume Associated With In-Hospital Mortality in Maintenance Dialysis Patients

INTRODUCTION: Accumulating evidence suggests that a large hospital volume (HV) is associated with favorable outcomes in various diseases or surgical procedures. The aim of this study is to clarify the correlation of HV and dialysis case volume (DCV) with in-hospital death in patients on maintenance dialysis. METHODS: The study cohort was derived from the Diagnosis Procedure Combination database, a national inpatient database in Japan, from 2012 to 2014. We included 382,689 admissions of maintenance dialysis patients over the age of 20 years in the analysis. HV was defined as the mean number of daily hospitalized patients, and DCV was defined as the mean number of annually hospitalized patients on maintenance dialysis. The primary outcome was in-hospital all-cause mortality, evaluated using multivariable logistic regression models across the respective quartiles of HV and DCV. RESULTS: The mean age of participants was 69 ± 12 years; 94% were receiving hemodialysis, and 21,182 patients (5.5%) died after hospitalization. In unadjusted models, larger HV and DCV were both associated with lower in-hospital mortality. However, this association remained significant only for DCV after adjustment for potential confounders, with multivariable-adjusted odds ratios of 0.82 (95% confidence interval [CI], 0.79–0.85), 0.76 (95% CI, 0.73–0.80), and 0.68 (95% CI, 0.65–0.72) for DCV 249 to 432, 433 to 713, and ≥714 (vs. ≤ 248) admissions per year, respectively. Multivariable subgroup analyses determined that this association was independent of age, sex, dialysis modality, Charlson Comorbidity Index, and emergency admission. CONCLUSION: Selective admission to hospitals with a large DCV may improve outcomes of dialysis patients.