Page 9 - Read Online

Bozzetti et al. Neuroimmunol Neuroinflammation 2021;8:1-13 I http://dx.doi.org/10.20517/2347-8659.2020.26 Page 5
[35]
storage, or disease duration . Actually, an attempt to identify specific diagnostic cut-offs for CSF, plasma,
[46]
and serum through a receiver operating characteristic analysis was reported in a recent prospective
phase IV study conducted with the aim of evaluating the effect of dimethyl-fumarate on NfL values. The
authors identified specific NfL cut-offs to discriminate between MS patients and healthy controls with a
100% specificity, i.e., 807.5 pg/mL (80% sensitivity) for CSF, 13.0 pg/mL (47% sensitivity) for plasma, and
[46]
15.6 pg/mL (43.2% sensitivity) for serum .
NfL levels correlate with disease activity at sampling
NfL levels have also been demonstrated to correlate with disease activity in RRMS patients, which is
commonly assessed using a combination of different surrogate biomarkers, including clinical parameters
such as relapse-rate, and MRI signs (i.e., the presence of gadolinium-enhancing lesions or new or
unequivocally enlarging T2 hyperintense lesions) . In particular, in one of the first attempts to correlate
[34]
NfL levels with disease activity, the authors demonstrated that CSF NfL values were significantly increased
[37]
2-3 months after a clinical relapse and tended to gradually decrease thereafter . This pioneer finding was
confirmed using more sensitive fourth-generation methods, which allowed the demonstration of increased
CSF/serum NfL concentrations in patients who experienced a relapse within 3 months before sample
[49]
collection, compared to those in remission . In addition, a robust association between NfL values and
radiological parameters of disease activity has been demonstrated. In particular, CSF/serum NfL levels
are significantly higher in patients with gadolinium-enhancing lesions [9,20,49] and with new or enlarging
T2 lesions [20,40,50] . Moreover, NfL concentration progressively increases in correlation with the number
[9]
[38]
of contrast enhanced lesions [9,38,50] and T2 lesion load detected in both brain and spinal cord . As for
correlations between NfL values and clinical measure of disability, a robust correlation has been reported
between NfL levels and EDSS score at sampling [9,35,38,49] . In a recent cross-sectional study performed on two
Swiss MS cohorts, serum NfL concentration at baseline emerged as an indicator of previous clinical disease
activity, being significantly associated with a relapse within 60 days before sampling, mean annual relapse
rate in the last 1 and 2 years, and with the probability of EDSS worsening during the last 6 and 12 months .
[9]
NfL levels have a role in the prediction of future disease activity
Attention has more recently been devoted to the possible prognostic role of NfL, to determine whether its
concentration could correlate with clinical and radiological biomarkers of future disease activity [9,40,45,47-49,51,52] ,
[54]
with treatment response [20,38,39,42,46,49,53] , and with progression to a secondary progressive course .

In particular, serum NfL levels at baseline have displayed a significant association with the number of
[40]
clinical relapses in the subsequent 18 months and consequently with an increase in annual relapse rate
[9]
at 1 and 2 years follow-up , supporting the value of this biomarker in predicting future disability. A strong
and independent correlation between serum NfL levels above the 90th percentile of healthy controls values
and EDSS worsening in the following 12 months was recently observed in a cohort including 189 patients
with RRMS, 70 progressive cases, and 259 healthy controls . Different studies have also confirmed a
[51]
significant association between high serum NfL values at baseline and radiological hallmarks of disease
activity/progression during the follow-up, i.e., new T2-lesions and brain volume loss during the subsequent
[51]
[48]
4 years and brain/spinal cord volume loss as measured after 2 and 5 years from blood sampling . In
particular, Barro et al. reported a correlation between the percentage of brain/spinal cord volume changes
[51]
and serum NfL levels, that in a multivariate model remained the only predictors of brain volume loss at
2 years follow-up.
NfL levels help to predict long-term outcome
The possible role of NfL in predicting long-term clinical and radiological outcome in RRMS patients has
been investigated assessing serum and/or CSF NfL values in the course of a phase 3 randomized placebo-
[47]
controlled trial of intramuscular interferon-beta . A robust association emerged between CSF NfL