Concentrations of neurofilament light (NfL) chain in blood can detect concussion, its severity and help predict recovery in patients with mild traumatic brain injury (TBI), new research indicates.

“Blood NfL may be used to aid in the diagnosis of patients with concussion or mild TBI [and] to identify individuals at increased risk of developing persistent postconcussive symptoms following TBI,” said lead author Pashtun Shahim, MD, PhD, National Institutes of Health Clinical Center, Bethesda, Md.

“This study is the first to do a detailed assessment of serum NfL chain and advanced brain imaging in multiple cohorts, brain injury severities, and time points after injury. The cohorts included professional athletes and nonathletes, and over time up to 5 years after TBI,” Dr. Shahim added.

The study was published online July 8 in Neurology.

Rapid indicator of neuronal damage

The researchers studied two cohorts of patients with head injuries. In the first, they determined serum and CSF NfL chain levels in professional Swedish ice hockey players (median age, 27 years), including 45 with acute concussion, 31 with repetitive concussions and persistent post-concussive symptoms (PCS), 28 who contributed samples during preseason with no recent concussion, and 14 healthy nonathletes.

CSF and serum NfL concentrations were closely correlated (r = 0.71; P < .0001). Serum NfL distinguished players with persistent PCS due to repetitive concussions from preseason concussion-free players, with an area under the receiver operating characteristic curve of 0.97. Higher CSF and serum NfL levels were associated with a higher number of concussions and severity of PCS after 1 year.

The second cohort involved 230 clinic-based adults (mean age, 43 years), including 162 with TBI and 68 healthy controls. In this cohort, patients with TBI had increased serum NfL concentrations compared with controls for up to 5 years, and these concentrations were able to distinguish between mild, moderate, and severe TBI. Serum NfL also correlated with measures of functional outcome, MRI brain atrophy, and diffusion tensor imaging estimates of traumatic axonal injury.

“Our findings suggest that NfL concentrations in serum offer rapid and accessible means of assessing and predicting neuronal damage in patients with TBI,” the investigators wrote.

What’s needed going forward, said Dr. Shahim, is “validation in larger cohorts for determining what levels of NfL in blood may be associated with a specific type of TBI, and what the levels are in healthy individuals of different ages.”

Not ready for prime time

In an accompanying editorial, Christopher Filley, MD, University of Colorado at Denver, Aurora, noted that NfL “may prove useful in identifying TBI patients at risk for prolonged symptoms and in enabling more focused treatment for these individuals.”

“These reports are richly laden with acute and longitudinal data that not only support the use of NfL as a convenient diagnostic test for TBI, but plausibly correlate with the neuropathology of TBI that is thought to play a major role in immediate and lasting cognitive disability,” he wrote.

Although the origin of TBI-induced cognitive decline is not entirely explained by traumatic axonal injury, “NfL appears to have much promise as a blood test that relates directly to the ubiquitous white matter damage of TBI, revealing a great deal about not only whether a TBI occurred, but also the extent of injury sustained, and how this injury may affect patient outcome for years thereafter,” Dr. Filley wrote.

However, he cautioned more research is needed before the blood test can be routinely applied to TBI diagnosis in clinical practice. “Among the hurdles still ahead are the standardization of measurement techniques across analytical platforms, and the determination of precise cutoffs between normal and abnormal values in different ages groups and at varying levels of TBI severity,” Dr. Filley noted.

The research was supported by the National Institutes of Health, the Department of Defense, the Center for Neuroscience and Regenerative Medicine at the Uniformed Services University, and the Swedish Research Council. Dr. Shahim and Dr. Filley have reported no relevant financial relationships.

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