Validation of the GCS−Pupil Scale in Traumatic Brain Injury: Incremental Prognostic Value of Pupillary Reactivity with GCS in the Prospective Observational Cohorts CENTER-TBI and TRACK-TBI

Abstract

To compare the incremental prognostic value of pupillary reactivity captured as part of the Glasgow Coma Scale–Pupils (GCS–P) score or added as separate variable to the GCS+P, in traumatic brain injury (TBI). We 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. Logistic regression was utilized to quantify the prognostic performances of GCS–P (GCS minus number of unreactive pupils) and GCS+P versus GCS alone according to Nagelkerke’s R ². End-points were mortality and unfavorable outcome (Glasgow Outcome Scale–Extended score 1–4) at 6 month post-injury. We estimated 95% confidence intervals (CIs) with bootstrap resampling to summarize the improvement in prognostic capability. In a meta-analysis of CENTER-TBI and TRACK-TBI, GCS as a linear score had a R ² of 25% (95% CI 19–31%) for mortality and 33% (4–41%) for unfavorable outcome. Pupillary reactivity as a separate variable improved the R ² by an absolute value of 6% (4.0–7.7%) and 2% (1.2–3.0%) for mortality and unfavorable outcome, respectively, while comparatively half of this improvement was captured by the GCS–P score (3% [2.1–3.3%], 1% [1–1.7%], respectively). GCS–P showed a stronger association with 6-month outcome after TBI than GCS alone and provides a single integrated score. However, this comes at a loss of clinical and prognostic information compared with GCS+P. For prognostic models, inclusion of GCS and pupillary reactivity as separate factors may be preferable to using a GCS–P summary score.