The Mayo classification system for traumatic brain injury severity

Purpose: To develop a single TBI severity classification system based on commonly used TBI severity measures and indicators that (1) maximally uses available positive evidence to classify TBI severity in three categories: (a) Moderate- evere (Definite) TBI, (b) Mild (Probable) TBI, ( c) Symptomatic (Possible) TBI; (2) reflects current clinical knowledge and relevance; and (3) classifies a larger number of cases than single indicator systems with reasonable accuracy. Main Findings: The study sample of a defined population consisted of 1501 unique Olmsted County residents with at least one confirmed TBI event from 1985 to 1999. Within the sample, 1678 TBI events were confirmed. Single measures of TBI severity were not available in a large percentage of these events, i.e., Glasgow Coma Scale (GCS) was absent in 1242 (74.0%); loss of consciousness, absent in 178 (70.2%), post-traumatic amnesia (PTA), absent in 974 (58.1%), head CT, not done in 827 (49.3%). The Mayo Classification System for TBI Severity was developed to classify cases based on available indicators that included death due to TBI, trauma-related neuroimaging abnormalities, GCS, PTA, loss of consciousness and specified post-concussive symptoms. Using the Mayo system, all cases were classified. For the Moderate- Severe ( Definite) TBI classification, estimated sensitivity was 89% and estimated specificity was 98%. Conclusions: By maximally using relevant available positive evidence, the Mayo system classifies a larger number of cases than single indicator systems with reasonable accuracy. This system may be of use in retrospective research and for determination of TBI severity for planning postacute clinical care.