The application of IMPACT prognostic models to elderly adults with traumatic brain injury: A population-based observational cohort study

Abstract

<p><i>Objective</i>: To examine the performance of the International Mission for Prognosis and Clinical Trial Design in Traumatic Brain Injury (IMPACT) prognostic models in older patients.</p> <p><i>Methods</i>: Using data from the National Study on Costs and Outcomes of Trauma (NSCOT), this study identified adult patients presenting to US hospitals in 2001 and 2002 with non-penetrating moderate or severe traumatic brain injury (GCS ≤ 12). IMPACT model calibration and discrimination in the older stratum (65–84 years) was compared to that in the younger stratum (18–64 years).</p> <p><i>Results</i>: IMPACT model discrimination did not differ significantly between the older (<i>n</i> = 202; weighted <i>n</i> = 268) and younger strata (<i>n</i> = 613; weighted <i>n</i> = 1632) and was generally adequate (c-statistic for the core-death model = 0.81 [0.77–0.84] vs 0.75 [0.66–0.84], respectively; <i>p</i> = 0.26). IMPACT model calibration was poor for both older and younger strata (Hosmer-Lemeshow <i>p</i>-value for the core-death model = 0.01 vs < 0.0001, respectively). Pre-specified qualitative graphical evaluation suggested substantial under-prediction of mortality in the oldest decades of life, but not among younger patients.</p> <p><i>Conclusions</i>: The examined IMPACT prognostic models demonstrated adequate discrimination and poor calibration in both older and younger patients, yet particular caution may be required when applying these models to the elderly.</p