Blood test detects mild traumatic brain injury for up to a week

By Lucy Piper

Researchers report findings of a blood biomarker that consistently detects mild to moderate traumatic brain injury (MMTBI) for up to 7 days and quantifies the degree of damage.

"This test could take the guesswork out of making a diagnosis by allowing doctors to simply look for a specific biomarker in the blood", lead researcher Linda Papa (Orlando Regional Medical Center, Florida, USA) told the press.

The biomarker is glial fibrillary acidic protein (GFAP) and is found in the astroglial skeleton of both white and grey brain matter.

Assessment of GFAP in 1831 blood samples from 584 patients aged 18 to 83 years attending a level I trauma centre showed that it was detectable within 1 hour of injury, peaked at 20 hours and steadily declined over 72 hours, but was still detectable at 7 days.

Four hours after injury, GFAP levels were significantly increased in the 325 patients with MMTBI (97.8% with Glasgow Coma Scale [GCS] score of 13 to 15) compared with the 259 without (GCS score=15) and remained consistently higher over the 19 distinct sampling time points up to 7 days, ranging from 0.008-8.078 ng/mL versus 0.008-0.773 ng/mL, respectively.

Over the course of the week, areas under the curve demonstrated that GFAP was 73% to 94% accurate in detecting MMTBI, the researchers report in JAMA Neurology.

The biomarker was also up to 97% accurate in detecting intracranial lesions, confirmed by computed tomography (CT) in 35 patients with MMTBI, and the need for neurological intervention, occurring in seven MMTBI patients, with up to 100% accuracy.

In a related editorial, Tanya Bogoslovsky and Ramon Diaz-Arrastia, both from the Uniformed Services University of the Health Sciences in Rockville, Maryland, USA, point out that the "longer half-life of GFAP and its ability to detect CT lesions within 7 days after injury make it useful in subacute settings, when the diagnosis of [mild] TBI with persistent symptoms incurred after concussion can be a particular challenge."

Papa and co-workers also assessed the blood biomarker ubiquitin C-terminal hydrolase L1 (UCH-L1), a neuronal protein, and while it showed diagnostic potential for MMTBI, intracranial lesions and neurological intervention, its accuracy alone and in combination with GFAP was exceeded by that of GFAP alone, particularly for distinguishing patients with MMTBI.

The researchers note that like GFAP, UCH-L1 was detectable within an hour after injury, but levels rose much more rapidly, peaking at 8 hours and declining over 48 hours, therefore the window for detecting MMTBI is much narrower.

"Accordingly, the early rise of UCH-L1 can be useful for detecting [mild] TBI in hyperacute (including both civilian and military) settings and may suitable for development of point-of-care testing", say Bogoslovsky and Diaz-Arrastia.

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