Many factors influence NfL level in CSF
The association between CNS level of NfL with age among healthy controls “implies that age-specific reference values may be needed and that the diagnostic potential of CSF NfL may decrease with age,” said the researchers. The finding that CSF NfL level was higher in men in a minority of diagnoses has uncertain clinical significance, they added. Sex-specific reference values may be needed.
Dr. Bridel and colleagues found that age, sex, and cohort explained 46% of variation in CSF level of NfL, which suggests that many factors that determine this level have yet to be identified. Disease duration and disease severity could influence the CSF level of NfL, but the data sets that the investigators analyzed did not include this information.
Because CSF NfL level did not differ significantly between relapsing/remitting MS, secondary progressive MS, and primary progressive MS, this biomarker “may not differentiate acute inflammation-induced neuronal damage in the context of relapses from progressive neurodegeneration if the consequences of recent relapses or novel lesion formation are not considered,” said Dr. Bridel and colleagues. The findings do suggest, however, that CSF level of NfL can distinguish FTD from other dementias, as well as Parkinson’s disease from atypical parkinsonian syndromes. Furthermore, it is possible that the findings of this study can be translated to serum level of NfL, said the authors.
One of the study’s limitations was that diagnosis was based on clinical criteria, said Dr. Bridel and colleagues. In addition, the authors were unable to identify dementia of multifactorial origin, which might have reduced the differences in CSF NfL level distributions between dementia subtypes. Finally, the authors only analyzed studies that relied on a specific immunoassay for CSF NfL level.
The authors reported receiving funding from various pharmaceutical and biopharmaceutical companies, as well as from grants and research foundations. The funders did not influence the study design, data analysis, or interpretation, however.
SOURCE: Bridel C et al. JAMA Neurol. 2019 June 17. doi: 10.1001/jamaneurol.2019.1534.