S100b Immunoassay: An Assessment of Diagnostic Utility in Minor Head Trauma

Diagnostic performance of S100B protein serum measurement in detecting intracranial injury in children with mild head trauma

OBJECTIVE

To assess the accuracy of S100B serum level to detect intracranial injury in children with mild traumatic brain injury.

METHODS

A multicenter prospective cohort study was carried out in the paediatric emergency departments of three tertiary hospitals in Switzerland between January 2009 and December 2011. Participants included children aged <16 years with a mild traumatic brain injury (GCS ≥13) for whom a head CT was requested by the attending physician. Venous blood was obtained within 6 h of the trauma in all children for S100B measurement before a head CT was performed. As the S100B value was not available during the acute care period, the patient's management was not altered. The main measures were protein S100B value and the CT result.

RESULTS

20/73 (27.4%) included children had an intracranial injury detected on CT. S100B receiver operating characteristics area under the curve was 0.73 (95% CI 0.60 to 0.86). With a 0.14 µg/L cut-off point, S100B reached an excellent sensitivity of 95% (95% CI 77% to 100%) and 100% (95% CI 81% to 100%) in all children and in children aged >2 years, respectively. The specificity, however, was 34% (95% CI 27% to 36%) and 37% (95% CI 30% to 37%), respectively.

CONCLUSIONS

S100B has an excellent sensitivity but poor specificity. It is therefore an accurate tool to help rule out an intracranial injury but cannot be used as the sole marker owing to its specificity. Used with clinical decision rules, S100B may help to reduce the number of unnecessary CT scans.

CT overuse for mild traumatic brain injury

BACKGROUND

Multiple, validated, evidence-based guidelines exist to inform the appropriate use of computed tomography (CT) to differentiate mild traumatic brain injury (MTBI) from clinically important brain injury and to prevent the overuse of CT. Yet, CT use is growing rapidly, potentially exposing patients to unnecessary ionizing radiation risk and costs. A study was conducted to quantify the overuse of CT in MTBI on the basis of current guideline recommendations.

METHODS

A retrospective analysis of secondary data from a prospective observational study was undertaken at an urban, Level I emergency department (ED) with more than 90,000 visits per year. For adult patients with minor head injury receiving CT imaging at the discretion of the treating physician, the proportion of cases meeting criteria for CT on the basis of the Canadian CT Head Rule (CCHR), American College of Emergency Physicians (ACEP) Clinical Policy, New Orleans Criteria (NOC), and National Institute for Health and Clinical Excellence (NICE) guidelines was reported.

RESULTS

All 346 patients enrolled in the original study were included in the analysis. The proportion of cases meeting criteria for CT for each of the guidelines was: CCHR 64.7% (95% confidence interval [CI], 0.60-0.70), ACEP 74.3% (95% CI, 0.70-0.79), NICE 86.7% (95% CI, 0.83-0.90), and NOC 90.5% (95% CI, 0.87-0.94). The odds ratio of the guidelines for predicting positive head CT findings were also reported.

DISCUSSION

Some 10%-35% of CTs obtained in the ED for MTBI were not recommended according to the guidelines. Successful implementation of existing guidelines could decrease CT use in MTBI by up to 35%, leading to a significant reduction in radiation-induced cancers and health care costs.