The predictive value of field versus arrival Glasgow coma scale score and TRISS calculations in moderate-to-severe traumatic brain injury

Background: Glasgow Coma Scale (GCS) scores are widely used to quantify level of consciousness in the prehospital environment. The predictive value of field versus arrival GCS is not well defined but has tremendous implications with regard to triage and therapeutic decisions as well as the use of various predictive scoring systems, such as Trauma Score and Injury Severity Score (TRISS). This study explores the predictive value of field GCS (fGCS) and arrival GCS (aGCS) as well as TRISS calculations using field (fTRISS) and arrival (aTRISS) data in patients with moderate-to-severe traumatic brain injury (TBI). Methods: Major trauma victims with head Abbreviated Injury Scores of 3 or greater were identified from our county trauma registry over a 16-year period. The predictive ability of fGCS with regard to aGCS was explored using univariate statistics and linear regression modeling. The difference between aGCS and fGCS was also modeled against mortality and the composite endpoint using logistic regression, adjusting for fGCS. The predictive value of preadmission GCS (pGCS), defined as either fGCS or aGCS in nonintubated patients without a documented fGCS, with regard to mortality and a composite endpoint representing the need for neurosurgical care (death, craniotomy, invasive intracranial pressure monitoring, or intensive care unit care > 48 hours) was determined using receiver-operator curve (ROC) analysis. Finally, fTRISS and aTRISS predicted survival values were compared with each other and to observed survival. Results: A total of 12,882 patients were included. Mean values for fGCS and aGCS were similar (11.4 and 11.5, respectively, p = 0.336), and a strong correlation (r(2) = 0.67, 95 % CI 0.66-0.69, p < 0.0001) was observed between them. The difference between fGCS and aGCS was also predictive of outcome after adjusting for fGCS. Good predictive ability was observed for pGCS with regard to both mortality and neurosurgical intervention. Both fTRISS and aTRISS predicted survival values were nearly identical to observed survival. Observed and fTRISS predicted survival were nearly identical in patients undergoing prehospital intubation. Conclusions: Values for fGCS are highly predictive of aGCS, and both are associated with outcome from TBI. A change in GCS from the field to arrival is highly predictive of outcome. The use of field data for TRISS calculations appears to be a valid methodological approach, even in severely injured TBI patients undergoing prehospital intubation.