Validation of the GCS-Pupil scale in Traumatic Brain Injury Incremental prognostic performance of pupillary reactivity with GCS in the prospective observational cohorts CENTER-TBI and TRACK-TBI

ObjectiveTo compare the incremental prognostic value of pupillary reactivity as captured in the GCS-Pupils score (GCS-P) or added as separate variable to the Glasgow Coma Scale (GCS) in traumatic brain injury (TBI). MethodsWe analyzed patients enrolled between 2014 and 2018 in the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI, n=3521) and the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI, n=1439) cohorts. We used logistic regression to quantify the prognostic performances of GCS-P versus GCS according to Nagelkerkes R2. Endpoints were mortality and unfavorable outcome (Glasgow Outcome Scale-Extended score 1-4) at 6 months after injury. We estimated 95% confidence intervals with bootstrap resampling to summarize the improvement in prognostic capability. ResultsGCS as a linear score had a R2 of 24% (95% confidence interval [CI] 17-30) and 30% (95%CI 17-43) for mortality and 29% (95%CI 25-34) and 38% (95%CI 29-47) for unfavorable outcome in CENTER-TBI and TRACK-TBI respectively. In the meta-analysis, pupillary reactivity as a separate variable improved the R2 by an absolute value of 6% and 2% for mortality and unfavorable outcome (95%CI 4.0-7.7 and 1.2-3.0, respectively), with half the improvement captured in the GCS-P score (3%, 95%CI 2.1-3.3 and 1%, 95%CI 1-1.7, respectively). ConclusionsGCS-P has a stronger association with outcome after TBI than the GCS alone. However, for prognostic models, inclusion of GCS and pupillary reactivity as separate scores is preferable.