Agreement Between Injury Severity Scores Calculation Methods Among Older Adults with Traumatic Brain Injury

Abstract

Research Objectives Medicare administrative data is a valuable resource for understanding post-acute care outcomes of older adults. However, these records lack information about injury severity that is useful for understanding post-acute care among those with TBI. The Injury Severity Score (ISS) reflects anatomic injury severity and is calculated by trauma registries, but can also be calculated from ICD-9 codes available in administrative data. Our objective is to examine the agreement between ICD-9 derived ISS scores and those sourced from trauma registries. Design Design: We linked Medicare administrative data to the National Trauma Data Bank (NTDB) using a Bayesian record linkage algorithm. We then examined the agreement between trauma registry- ISS scores and those calculated from acute and post-acute ICD-9 codes using Injury Categorization Software (ICDPIC) software. Setting U.S. Inpatient Rehabilitation Facilities (IRF) and Skilled Nursing Facilities (SNF). Participants Medicare beneficiaries who discharged to a SNF or an IRF following hospitalization for TBI between 2011 and 2015. Interventions N/A. Main Outcome Measures Injury Severity Score. Results For scores derived from acute claims, the absolute agreement with trauma registry scores was 11.2% (8.3, 14.2), with 41.8% (37.4, 46.2) of scores being within +/- 5 points. Trauma registry sourced ISS scores were more often higher than the ISS from the trauma registry. In the majority of cases ISS scores could not be calculated from post-acute claims, due to a lack of injury specific ICD-9 codes. Conclusions There is limited agreement between trauma registry ISS scores and those calculated from the ICD-9 codes of acute claims. The scores derived from acute claims may have utility for adjustment, but may underestimate anatomic injury severity of older adults with TBI. Post-acute claims lack the detailed injury codes required for calculation of ISS scores. Author(s) Disclosures Co-author Roee Gutman has served as an expert witness for Johnson & Johnson. The authors have no other conflicts of interest to report. Medicare administrative data is a valuable resource for understanding post-acute care outcomes of older adults. However, these records lack information about injury severity that is useful for understanding post-acute care among those with TBI. The Injury Severity Score (ISS) reflects anatomic injury severity and is calculated by trauma registries, but can also be calculated from ICD-9 codes available in administrative data. Our objective is to examine the agreement between ICD-9 derived ISS scores and those sourced from trauma registries. Design: We linked Medicare administrative data to the National Trauma Data Bank (NTDB) using a Bayesian record linkage algorithm. We then examined the agreement between trauma registry- ISS scores and those calculated from acute and post-acute ICD-9 codes using Injury Categorization Software (ICDPIC) software. U.S. Inpatient Rehabilitation Facilities (IRF) and Skilled Nursing Facilities (SNF). Medicare beneficiaries who discharged to a SNF or an IRF following hospitalization for TBI between 2011 and 2015. N/A. Injury Severity Score. For scores derived from acute claims, the absolute agreement with trauma registry scores was 11.2% (8.3, 14.2), with 41.8% (37.4, 46.2) of scores being within +/- 5 points. Trauma registry sourced ISS scores were more often higher than the ISS from the trauma registry. In the majority of cases ISS scores could not be calculated from post-acute claims, due to a lack of injury specific ICD-9 codes. There is limited agreement between trauma registry ISS scores and those calculated from the ICD-9 codes of acute claims. The scores derived from acute claims may have utility for adjustment, but may underestimate anatomic injury severity of older adults with TBI. Post-acute claims lack the detailed injury codes required for calculation of ISS scores.