Capture rates of comorbidity measures at inpatient rehabilitation facilities after a stroke or brain injury.

BACKGROUND: Comorbidity indices have been used to represent the overall medical complexity of patient populations in clinical research; however, it is not known how well they capture the comorbidities of patients with a stroke or brain injury admitted to inpatient rehabilitation facilities (IRFs). OBJECTIVE: To determine how well commonly used comorbidity indices capture the comorbidities of patients admitted to IRFs after a stroke or brain injury. DESIGN: Cross-sectional, retrospective study. SETTING: IRFs nationwide. PARTICIPANTS: Adults from four impairment groups: (1) hemorrhagic stroke, (2) ischemic stroke, (3) nontraumatic brain injury (NTBI), and (4) traumatic brain injury (TBI). MAIN OUTCOME MEASURES: International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) codes were extracted from the Uniform Data System for Medical Rehabilitation (UDSMR) for IRF discharges from October 1, 2015 to December 31, 2017. The percentage of discharges captured by Deyo-Charlson, Elixhauser, and Centers for Medicare and Medicaid Services (CMS) tiers was determined, as was the percentage of comorbidities captured. These measures were also compared with respect to their ability to capture chronic medical complexity by examining the percentage of codes captured after removal of codes deemed to represent hospital complications or sequela of the admission diagnosis. RESULTS: The percentage of discharges without at least one ICD-10-CM code captured by any index ranged from 0.3%-3.8%. The percentage of comorbidities with a prevalence exceeding 1% captured by at least one index ranged from 37.1%-43.6%. Chronic comorbidities were most likely to be captured by Elixhauser (40.7%-44.4%), followed by Deyo-Charlson (7.8%-9.6%), then CMS tiers (4.5%-6.9%). Existing comorbidity measures capture most IRF discharges related to a brain injury or stroke, whereas most medical comorbidities escape representation. Several common, functionally relevant diagnoses were not captured. CONCLUSION: The use of comorbidity indices in the IRF neurologic injury population should account for the fact that these measures miss several common, important comorbidities.

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

OBJECTIVE: To examine whether commonly used comorbidity indexes (Deyo-Charlson comorbidity index, Elixhauser comorbidity index, 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 spinal cord injury (SCI) (Medicare-established Impairment Group Codes 04.110-04.230, 14.1, 14.3). This study included SCI discharges (N=66,235) from 833 inpatient rehabilitation facilities. MAIN OUTCOME MEASURES: International Classification of Diseases-10th Revision-Clinical Modifications (ICD-10-CM) codes were used to assess 3 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 men 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% confidence interval, 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.