Background/Purpose: Individuals with systemic lupus erythematosus (SLE) have an increased risk of hospitalization throughout their lifetime, potentially leading to higher patient mortality and healthcare costs. Establishing minimum volume thresholds for other medical and surgical conditions has been proposed as a way to improve outcomes. We evaluated the relationship between a hospital’s yearly SLE volume and two outcomes: mortality and cost of hospitalization.

Methods: We used the National Inpatient Sample (NIS), which after weighting provides annual estimates for more than 35 million community hospitalizations in the US. Analysis was limited to adults without missing relevant variables hospitalized in 2017. Admissions with SLE were captured in ICD-10-CM codes (M32.1x, M32.8, M32.9). Hospital specific costs were obtained using NIS cost-to-charge ratio files. We used linear regression to model average cost for admissions with a diagnosis of SLE based on the number of yearly SLE discharges at the treating hospital (analysis conducted with continuous variable of SLE volume per year, and repeated with a categorical variable establishing 50 or more SLE discharges yearly), controlling for the Ward systemic lupus-specific risk adjustment index¹ modified for ICD-10, demographics (age, sex, race/ethnicity), health insurance, income quartile in the ZIP Code of residence, and hospital characteristics (bed size, rural/urban/teaching status). In addition, we used Poisson regression to model mortality risk based on hospital SLE volume and the covariates listed above. All analyses accounted for the complex sampling design of the NIS.

Results: Adults with SLE included in the analysis accounted for a nationally estimated 172,135 discharges in 2017 (0.48% of all hospital discharges). Mean cost per SLE discharge was $14,420 (SE $207); 2% of hospitalizations resulted in death. In adjusted analysis, cost per SLE discharge was higher for hospitals caring for more SLE patients per year. Approximately 18.6% of included hospitals had a yearly SLE volume greater than 50. Hospitals with a yearly SLE volume greater than 50 had a higher average cost per SLE discharge compared to those with an SLE volume less than 50 (cost difference $3,399; 95% CI $1,803 to $4,996). Risk of inpatient mortality did not significantly vary based on SLE hospital volume.

Conclusion: Higher yearly SLE hospital volume was associated with greater cost per discharge, without significant differences in mortality rates compared to hospitals with lower SLE volumes. If the lupus-specific risk adjustment index we used does not fully capture patient disease severity or if there were coding differences between hospitals, this could have potentially affected the results. Our findings do not suggest a minimum volume threshold for SLE care that can be used to improve inpatient outcomes.

Reference: 1. Ward, MM. Development and testing of a systemic lupus-specific risk adjustment index for in-hospital mortality. J Rheumatol 2000; 27(6):1408-1413.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/mortality-and-cost-of-hospitalization-do-hospitals-caring-for-more-sle-patients-perform-better/