Introduction Biochemical markers may have a role to play as objective tools for ruling out significant complications following minor head injury, while reducing the rate of ‘unnecessary’ CT scans. This study aimed to systematically identify and analyse the data from studies investigating biochemical markers as a screening tool for intracranial injury on CT.

Methods Potentially relevant studies were identified by an electronic search of key databases including MEDLINE, EMBASE and CINAHL. Papers in English were included if they consisted of a cohort of more than 20 patients with more than 50% having suffered a minor head injury (GCS 13–15). Studies must describe the use of a biochemical marker to screen for the identification of intracranial or neurosurgical injury.

Results A total of 7800 citations were identified of which 13 were included. Ten of these were investigating the role of protein S100B, two Neuron-Specific Enolase and one for dopamine and epinephrine. No useful, validated data could be extracted from the non-S100B studies. Mild head injury (GCS of 13–15) was generally consistently defined and included mild symptoms. All recruited patients received the reference standard of CT scan, mostly within 6 h of injury, along with the index test. Analysis techniques varied but are now practical for real-time results in the ED. Meta-analysis of these pooled data gives a sensitivity of 97.7% (95% CI 95.1% to 99.3%) and specificity of 43.4% (95% CI 31.4% to 56.2%) with a negative likelihood ratio of 0.053 (95% CI 0.015 to 0.117).

Discussion There is a mounting body of evidence to support the addition of protein S100B as a triage tool for CT, in minor head injury patients, within 4 h of their injury. While the quality of studies so far is good, results are mixed and the marker needs further testing in conjunction with clinical decision rules.