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. 2025 Jul 1;272(7):484.
doi: 10.1007/s00415-025-13222-w.

Insight into NeuroCOVID: neurofilament light chain (NfL) as a biomarker in post-COVID-19 patients with olfactory dysfunctions

Fiorenza Pennacchia #  1 , Federica Zoccali #  1   2 , Carla Petrella #  3 , Giuseppina Talarico  4 , Eqrem Rusi  4 , Maria Antonella Zingaropoli  5 , Wael Abu Ruqa  1 , Giuseppe Bruno  4 , Rosamaria Capuano  6   7 , Alexandro Catini  6   7 , Corrado Di Natale  6   7 , Antonio Minni  1   2 , Christian Barbato  8
Affiliations

Insight into NeuroCOVID: neurofilament light chain (NfL) as a biomarker in post-COVID-19 patients with olfactory dysfunctions

Fiorenza Pennacchia et al. J Neurol. .

Abstract

The term NeuroCOVID was coined to describe the neurological consequences observed in COVID-19 patients. Numerous patients infected with SARS-CoV-2 reported olfactory dysfunction as the first symptom preceding clinical manifestations, such as cough and fever, or even the only symptom, suggesting the sudden loss of smell or hyposmia as an important predictive factor for COVID-19 infection. Several patients developed long-term olfactory impairment, but to date there is not available a biochemical diagnosis of anosmia. The aim of this pilot study is to investigate the association between neurofilament light-chain (NfL) serum levels and the olfactory dysfunctions in post-COVID-19 patients. This study recruited patients who developed COVID-19 between January 2020 and August 2021. They were evaluated between October 2022 and March 2023 by Sniffin' Sticks tests to investigate deficits of odor identification, discrimination, and threshold and serum NfL biomarker measurement to assess a neuronal damage. Out of 27 patients, 11 were affected by post-viral permanent olfactory dysfunction (named Od-post-COVID-19) and 16 healed from the infection without residual Od problem, as a control group. We observed an increased levels of NfL 16.02 ± 1.91 pg/mL in Od-post-COVID-19, suggesting that NfL to be recognized as a biomarker of post-viral olfactory dysfunction, supporting the diagnostic process of NeuroCOVID, joined with other well-known neurological biomarkers and/or innovative investigative approaches.

Keywords: Anosmia; COVID-19; Long COVID; Nasal mucosa; Neuro-olfactory epithelium; NeuroCOVID; Neurofilament light chain (NfL); Olfactory dysfunction.

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Conflict of interest statement

Declarations. Conflicts of interest: The authors declare no conflicts of interest. Institutional review board statement: The study was conducted according to the Declaration of Helsinki and followed the Institutional Review Board standards of the Sapienza University of Rome, Policlinico Umberto I (ethical committee Ref. 6536). Informed consent: Informed consent was obtained from all subjects involved in the study.

Figures

Fig. 1
Fig. 1
Serum NfL levels in controls and Od-post-COVID-19 patients. *p < 0.01
See this image and copyright information in PMC

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