Blood test reduces risk for brain injury patients

Costly CT scans and associated radiation exposure may be avoided in patients with suspected traumatic brain injury (TBI) thanks to a high-sensitivity blood test.

The blood test might help doctors rule out traumatic intracranial injuries like brain haemorrhage and contusion before resorting to CT scanning, according to a new trial.

The novel blood test was administered within 12 hours of a suspected TBI, and measured levels of two biomarker proteins which are released into the bloodstream following a brain injury. The test correctly identified 99.6% of patients who did not have a traumatic intracranial injury on head CT scans among over 1900 adults (mostly with mild TBI) presenting to emergency departments in the USA and Europe.

Current practice for mild TBI involves a series of checklists of symptoms and signs — known as clinical decision rules — that a treating physician will look for to decide whether a CT scan is necessary. One of the most important clinical guides for determining the need for a CT scan is the patient’s initial level of alertness — measured using the Glasgow Coma Scale (GCS) score — with some guidelines recommending a head CT for anyone with a less than perfect GCS score of 15.

The blood test investigated in this study was able to predict which patients did not have a brain injury visible on CT scan with very high accuracy, even among those with a GCS less than 15. Further research to determine the extent to which the biomarker test complements decision rules, and as well as its impact on healthcare costs and patient throughput, will be key to understanding the test’s usefulness in clinical practice.

“Routine use of the new biomarker test in emergency departments could reduce head CT scans by a third in acutely head injured patients,” said research co-leader Dr Jeffrey Bazarian, from the University of Rochester School of Medicine in Rochester, New York.

“Our results suggest that patients with mild TBI (initial GCS of 14 or 15) who have no other indication for a CT (such as a focal neurologic deficit), and who have a negative test, can safely avoid a CT scan.”

Based on early, unpublished results of the study, the US Food and Drug Administration has approved the commercial use of this blood-based brain biomarker test, making it the first clinically approved test of its kind in North America.

Current TBI practice

TBI occurs when an external force such as a bump or blow to the head disrupts the normal function of the brain. Leading causes include falls, motor vehicle accidents and assaults. An estimated 54–60 million people worldwide suffer a TBI every year.

Currently, doctors use CT scans to detect traumatic intracranial injuries, usually bleeding, which sometimes require immediate neurosurgery. Over 20 million head CT scans are performed each year in the US alone. However, CT scans reveal such injures in less than 10% of those with milder head injuries, which make up three-quarters of all TBIs, and there is concern about the high radiation dose associated with CT scans of the head which can increase the risk of cancer.

Previous research has highlighted the potential of blood-based brain injury biomarkers to predict patients at high risk of intracranial injuries and in need of CT scanning. S100B is a well-accepted biomarker for TBI and is already in clinical use in Europe. Two other proteins — ubiquitin C-terminal hydrolase-L1 (UCH-L1) and glial fibrillary acidic protein (GFAP) — have also emerged as promising predictors of head CT results in small studies.

The authors note several limitations, including that the study did not evaluate the test’s predictive ability for clinical outcomes such as prolonged post-concussive symptoms, cognitive impairment and decreased functional status. They also note that it did not attempt to assess the test’s diagnostic accuracy compared with currently used biomarkers (ie, S100B) and clinical decision rules for triaging CT scanning. Finally, the sensitivity analysis comparing the diagnostic performance of the biomarker test for each of the proteins separately suggested that GFAP alone might perform as well as the two proteins combined, and requires further validation.

The multicentre observational trial has been published in The Lancet Neurology.

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