Assessing the Ability of Comorbidity Indexes to Capture Comorbid Disease in the Inpatient Rehabilitation Spinal Cord Injury Population.

Abstract Objective To examine whether commonly used comorbidity indexes (Deyo-Charlson comorbidity index, Elixhauser comorbidity index, and the Centers for Medicare and Medicaid Services (CMS) comorbidity tiers) capture comorbidities in the acute traumatic and nontraumatic SCI inpatient rehabilitation population. Design Retrospective cross-sectional study Participants Data were obtained from the Uniform Data System for Medical Rehabilitation from October 1, 2015 to December 31, 2017 for adults with SCI (Medicare-established Impairment Group Codes 04.110-04.230, 14.1, 14.3). This study included 66,235 SCI discharges from 833 inpatient rehabilitation facilities. Main Outcome Measure(s) International Classification of Diseases, 10th Revision, (ICD-10-CM) codes were used to assess three comorbidity indexes (Deyo-Charlson comorbidity index, Elixhauser comorbidity index, CMS comorbidity tiers). The comorbidity codes that occurred with >1% frequency were reported. The percentages of discharges for which no comorbidities were captured by each comorbidity index were calculated. Results Of the total study population, 39,285 (59.3%) were male and 11,476 (17.3%) were tetraplegic. The mean number of comorbidities was 14.7. There were 13,939 distinct ICD-10-CM comorbidity codes. There were 237 comorbidities that occurred with >1% frequency. The Deyo-Charlson comorbidity index, Elixhauser comorbidity index, and the CMS tiers did not capture comorbidities of 58.4% (95% CI 58.08-58.84), 29.4% (29.07-29.76), and 66.1% (65.73-66.46) of the discharges in our study, respectively, and 28.8% (28.42-29.11) of the discharges did not have any comorbidities captured by any of the comorbidity indexes. Conclusion Commonly used comorbidity indexes do not reflect the extent of comorbid disease in the SCI rehabilitation population. This work suggests that alternative measures may be needed to capture the complexity of this population.