Applying the Sliding Scale Approach to Quantifying Functional Outcomes up to Two Years After Severe Traumatic Brain Injury.

Abstract

Outcomes after severe traumatic brain injury can be represented by a sliding score that compares actual functional recovery to that predicted by illness severity models. This approach has been applied in clinical trials because of its statistical efficiency and interpretability but has not been used to describe change in functional recovery over time. The objective of this study was to use a sliding scoring system to describe magnitude of change in Glasgow Outcome Scale Extended (GOSE) at 6-, 12- and 24-months after severe TBI and to compare patients who improved after 6-months to those who did not. This study included consecutive severe TBI patients (Glasgow Coma Scale8; n=482) from a single center. We grouped patients into four strata based on probability of unfavorable outcome (GOSE=1-4) using the IMPACT model, selected a dichotomous GOSE threshold within each strata, compared each patient's GOSE to this threshold to calculate a score (GOSE-SS) from -5 to +4 at 6, 12, and 24 months. We compared GOSE-SS at 6-months to GOSE-SS at 12- and 24-months and characteristics of participants who improved after 6-months to those who did not using chi-square and t-tests. Compared to 6-months, 40% of patients (n=74) had improved GOSE-SS at 12-months and 53% had improved by 24-months (n=72). Among those who improved at 12-months, the average magnitude of improvement was 1.70.9 magnitude improvement and among those who improved at 24-months, the average magnitude was 1.91.0. Those who improved GOSE-SS score from 6 to 24-months had longer hospital stays (mean-difference=8.6 days; p=0.03), longer ICU stays (mean-difference=5.5 days; p=0.02), and longer ventilator time (mean-difference=5 days; p=0.02) compared to those who worsened. These results support an optimistic long-term outlook for severe TBI patients and emphasize the importance of long-term follow up in severe TBI survivors.