Can Neurofilament Light Chain (NfL) be used to diagnose ALS?

The protein neurofilament light chain (NfL) can be detected in blood serum and cerebrospinal fluid (CSF) using special analysis methods. More than 80 % of ALS patients show an increase in the serum or cerebrospinal fluid concentration of NfL. The increase particularly affects patients with a medium or higher rate of progression. Despite this correlation, the conclusion from an increased NfL value to the diagnosis of ALS is not permissible. It should be borne in mind that NfL can also be detected in numerous other neurological diseases (dementia, multiple sclerosis, Parkinson’s disease, etc.).

However, in ALS – compared to many other neurological diseases – the concentration is more elevated. Due to the limited specificity of NfL, expert medical interpretation of the findings is essential.