The csfdiscovery43 cerebrospinal fluid (CSF) multiplex assay is for central nervous system (CNS) biomarker discovery and qualification. The assay simultaneously measures 43 human CSF proteins that are thought to have potential as biomarkers in CNS diseases, particularly Alzheimer and Parkinson diseases, multiple sclerosis, and ALS. The assay is based on a multiple reaction monitoring mass spectrometry platform and generates reproducible data that firms can use in their drug and diagnostic development programs. In addition, the assay can be used for early-stage biomarker discovery and qualification in other disease areas such as traumatic brain injury.