A protein called serum neurofilament light chain (sNfL) shows promise as a biomarker to rapidly differentiate patients with primary psychiatric disorders from those with neuropsychiatric conditions such as dementia or delirium, according to a study issued in The Journal of Neuropsychiatry and Clinical Neurosciences.
“Accurate and timely diagnosis of neuropsychiatric disorders is critical because they require prompt and specific treatment to prevent further deterioration,” wrote Hamza Zarglayoun, B.Sc., of McGill University in Montreal, and colleagues. “However, making this distinction can be challenging in the psychiatric emergency department setting because of time constraints and the limited availability of diagnostic tools.”
Zarglayoun and colleagues zeroed in on sNfL, a protein that is released from damaged neurons into the cerebrospinal fluid and blood in response to brain injury or neurodegeneration. The researchers collected blood samples from 846 patients with psychiatric disorders and 20 patients with neuropsychiatric disorders who were admitted to a psychiatric emergency department; all diagnoses were determined over the course of the patients’ stay and later re-confirmed via chart review by two psychiatrists. The researchers then measured participants’ sNfL levels and compared results from the two groups.
Overall, sNfL levels were 72% higher among patients with neuropsychiatric disorders compared with those with psychiatric illnesses. After adjusting the data to account for patients’ age and sex, researchers still found significant association between sNfL levels and diagnostic group. They suggested a cutoff value of sNfL of 30.6 pg/mL—about three times the mean value of healthy adults—for optimal sensitivity and specificity.
A significant limitation of the study was the small number of patients with neuropsychiatric disorders relative to those with psychiatric illness—an imbalance that might have skewed the results. In addition, because the patients with neuropsychiatric disorders in their sample were older than those with primary psychiatric disorders, this age difference may have caused our threshold estimates to have higher accuracy, given that sNfL levels increase with age.
“Although further prospective research is needed to replicate these findings and validate the use of this sNfL cutoff in real-life settings before any widespread adoption, these results suggest that sNfL could be a valuable adjunct in the diagnostic process across a broad range of disorders,” the researchers wrote