Biomarkers in the clinical diagnosis and management of traumatic brain injury

Traumatic brain injury (TBI) is the leading cause of death and disability among young adults. Numerous safety improvements in the workplace, the addition of airbags to vehicles, and the enforcement of speed limits have all helped to reduce the incidence and severity of head trauma. While improvements in emergency response times and acute care have increased TBI survivability, this has heightened the necessity for developing reliable methods to identify patients at risk of developing secondary pathologies. At present, the primary clinical indicators for the presence of brain injury are the Glasgow Coma Scale (GCS), pupil reactivity, and head computed tomography (CT). While these indices have proven useful for stratifying the magnitude and extent of brain damage, they have limited utility for predicting adverse secondary events or detecting subtle damage. Biomarkers, reflecting a biological response to injury or disease, have proven useful for the diagnosis of many pathological conditions including cancer, heart failure, infection, and genetic disorders. For TBI, several proteins synthesized in astroglial cells or neurons have been proposed as potential biomarkers. These proteins include the BB isozyme of creatine kinase (CK-BB, predominant in brain), glial fibrilary acidic protein (GFAP), myelin basic protein (MBP), neuron-specific enolase (NSE), and S100B.The presence of these biomarkers in the cerebrospinal fluid and serum of patients with moderate-to-severe TBI, and their correlation with outcome, suggest that they may have utility as surrogate markers in clinical trials. In addition, many of these markers have been found to be sensitive indicators of injury, and therefore may have the potential to diagnose persons with mild TBI. In addition to biomarkers that correlate with long-term outcome, a few studies have identified prognostic biomarkers for secondary injury that may be useful in individualizing patient management.

Mass concentration measurements of creatine kinase BB isoenzyme as an index of brain tissue damage

A new two-site immunoenzymometric method using monoclonal antibodies was developed for measuring CK-BB mass concentrations in cerebrospinal fluid (CSF). Within- and between-assay coefficient of variation values for the method varied between 6 and 9%. Assay results are not affected by presence of sulfate and sialic acid groups on the enzyme. In comparison to catalytic activity measurements, a steady decline in the enzyme's specific activity was observed after acute head trauma. Repetitive measurements of CK-BB mass concentration in cerebrospinal fluid during the first 24 h after trauma enabled the estimation of brain lesion size. Clinical outcome of acute head trauma patients evaluated by Glasglow Outcome Scale, correlated well with cumulative CK-BB release after trauma. Also in neonates, CK-BB determinations in CSF correlated well with clinical findings.