The effect of comorbidity on hospital mortality in patients with SLE from an Asian tertiary hospital

Objectives: The objective of the study was to assess the disease burden of systemic lupus erythematosus (SLE) and the usefulness of the Charlson Comorbidity Index (CCI) as riskadjusted hospital mortality predictors in patients with SLE using a hospital administrative database. Methods: A historical cohort study of a hospital discharge database from 2004 to 2011 was used to identify cases with SLE and comorbidity using the International Statistical Classification of Diseases and Related Health Problems, ninth revision, Australian modification (ICD-9-AM) codes. Results: Over the eight years, 841 patients met the criteria of SLE with a hospital mortality rate of 9.2%. The hospital mortality rates (2.4%, 15.7%, 25.0%, and 30.4%, respectively, p<0.001) and hospital length of stay (geometric mean, 3.5, 5.6, 8.8, and 7.5 days, respectively, p<0.001) were consistently increased for patients with CCI ranging from none, low, moderate to high grade, respectively. Cox proportional hazards model analysis showed that CCI (hazard ratio (HR) 7.8 high vs. none, p<0.001) and infectious disease (HR 2.0, p=0.016) were significant and independent predictors of hospital mortality. Similar results were also seen with hospital length of stay by zero-truncated negative binomial regression model analysis. Conclusion: The SLE burden is high in this population. Comorbidities and infectious disease were some of the most important contributors to hospital mortality and resource utilization.