Association of neuronal injury blood marker neurofilament light chain with mild-to-moderate COVID-19, 2020, Ameres et al

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345451/
Markus Ameres, Susanne Brandstetter, Antoaneta A. Toncheva, Michael Kabesch, David Leppert, Jens Kuhle, Sven Wellmann
Germany and Switzerland
(doesn't have an abstract)

Even though the coronavirus disease 2019 (COVID-19) affects primarily the respiratory system some reports describe nervous system involvement as well [1–3]. Headache and anosmia have been frequently described as neurological symptoms of mild-to-moderate COVID-19 but a direct impact of COVID-19 on neuronal integrity has not been clarified yet [4]. Therefore, a neuronal biomarker would be extremely useful to elucidate neuro-axonal injury during an infection with Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and in the post-infection follow-up period. Serum neurofilament light chain (sNfL) has recently been considered as a specific biomarker to quantitate neuro-axonal damage in several disorders of the peripheral and central nervous system [5]. Hence, sNfL might also serve as a sensitive screening and follow-up marker for neuronal injury in COVID-19 patients.

We conducted a prospective cohort study in 100 healthcare workers (84 females, 16 males) following a COVID-19 outbreak in a major German children's and women's hospital [6]. The Ethics Committee of the University of Regensburg approved the study (file-number: 20-1767-101), and written informed consent was obtained from all study participants. They were categorized according to their SARS-CoV-2 infection status, n = 28 tested positive, n = 72 negative in PCR-based viral RNA amplification from nasopharyngeal swabs (Xpert© Xpress SARS-CoV-2, Cepheid) [5]. To preserve anonymity of study participants, age was assessed in three categories (18–35 years n = 33, 36–50 years n = 37 and 51–65 years n = 30) [7]. sNfL concentrations were measured using the single molecule array (Simoa) NF-light® kit on the HD-X Analyzer (Quanterix, Lexington, MA) [5]. First, descriptive statistics were calculated. Then, a multivariable linear regression model was fitted with sNfL as dependent variable and with sex, age and COVID-19 status as independent variables.

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Our results from a study in health care workers without known co-morbidities indicate that mild-to-moderate COVID-19 is associated with increased sNfL levels. Neurologic symptoms and complications in patients with SARS-CoV-2 infection have been reported by the first available studies during SARS-CoV-2 pandemic [1, 2]. However, these studies are restricted to hospitalized patients and, therefore, represent a population more likely to have severe neurological manifestations for a variety of reasons. Our results indicate for the first time that COVID-19 may affect the neuro-axonal integrity also in adults with a mild-to-moderate course of the disease. This new evidence for a more general neuro-destructive capability of SARS-CoV-2 also in mild-to-moderate COVID-19 patients should raise awareness for potential long-term neurologic sequelae following COVID-19.
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All Covid-19 cases were mild to moderate. The authors report that

NfL values are known to increase with age.