The role of neurofilament light chain in COVID‑19: A potential prognostic biomarker.

Coronavirus disease 2019 (COVID‑19) is an unprecedented global health concern that was declared a pandemic in March 2020. Although primarily recognized by respiratory symptoms, growing evidence suggested the causal relationship between the infection with the disease agent, namely severe acute respiratory coronavirus 2 (SARS‑CoV‑2), and neurological manifestations. Given that the virus‑induced neurological involvement is associated with a poorer prognosis, persistent neurological sequelae, and a more severe form of the disease, efforts have been made to introduce a biomarker to recognize neurological abnormalities early in the course of the disease. Studies indicate a significantly higher concentration of neurofilament light chain (NFL) in cerebrospinal fluid or blood of COVID‑19 patients versus adjusted controls. It has also been reported that COVID‑19 patients suffering from the severe form of the disease had higher NFL levels than patients with mild to moderate forms. Moreover, elevated NFL levels at hospital admission in patients who did not present primarily with neurological expressions could predict the emergence of neurological symptoms during the hospital stay. The early recognition of neurological abnormalities using the NFL biomarker could lead to escalated medical care limiting the progression of SARS‑CoV‑2‑induced central nervous system pathogenesis, resulting in a significant amelioration in disease outcome. Nevertheless, NFL assessment integrated with the evaluation of other neurodegenerative biomarkers and factors indicating disease prognosis could provide a more comprehensive estimate of disease prognosis and the extent of neurological involvement.