When mild is severe-contradictions in TBI classification using GCS and PTA
by: Drs. Olli Tenovuo and Anu Makinen; Department of Neurolgy University of Turku, Finland
Objectives: The relationship between the Glasgow Coma Scale (GCS) and the duration of post- traumatic amnesia (PTA) is poorly known. The purpose of this work was to study the eventual inconsistency in TBI classification using the GCS and the duration of PTA and to study the eventual reasons for discordant classifications using these two measures.
Method: A sample of 95 TBI patients, selected randomly from a database of 1029 TBI patients treated at a neurological outpatient university clinic during the years 1993-2005. The analysed data included TBI severity using GCS and PTA, age, gender, former TBIs, type of injury, education years, pre-traumatic psychiatric history, alcohol use and the presence of confounding factors in assessing GCS and/or PTA.
Results: The following classifications were used: GCS 3-8 = severe, 9-13 = moderate and 14-15 = mild TBI and PTA > 7 days = severe, 1-7 days = mode- rate and < 24 hours= mild TBI. Using these scales, the GCS and PTA yielded discordant classification of severity in 48.9% of patients and, in 91 % of these, PTA suggested a more severe injury. A difference of two classes of severity (= mild vs. severe) was found in 12.8% of patients. When the patients were divided into two groups, with concordant or discordant severity, the groups were similar in respect to age, gender, previous TBIs, psychiatric history, type of injury, alcohol use and the presence of confounding factors, but the number of highly educated persons was lower in the group with discordant assessment (P=0.01).
Conclusions: Although GCS and PTA are the most common measures to classify the severity of TBI, their relationship has been poorly characterized. In several studies, PTA has been a more reliable predictor of long-term cognitive sequels. This study supports the view that they describe clearly different aspects of TBI and that they may give clearly discordant assessments in a significant portion of patients. Pre-injury or injury-related factors do not seem to explain this discordance, which suggests that there is a certain fairly common type of injury, where consciousness is well preserved, but where the PTA may be long as a sign of more severe injury. The classification of TBI severity based solely on GCS is clearly inadequate and probably one of the main reasons for the conflicting views of the outcome in `mild' TBIs.
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