Are the NfL analyses in blood and cerebrospinal fluid equivalent?

The analysis of neurofilament light chain in blood and cerebrospinal fluid is not equivalent, but shows a close correlation. NfL concentrations are significantly higher in cerebrospinal fluid due to its proximity to the central nervous system (around 50-100 times higher). However, the necessary lumbar puncture is invasive and not suitable for regular follow-up.

As the values in the blood correlate with those in the CSF, blood sampling is more practical and sufficient for clinical routine. The less invasiveness and simple repeatability make NfL determination in blood a preferred method.