Table 1:
Biomarker categories and definitions
| Definition | Application to isolated RBD | |
|---|---|---|
|
| ||
| Diagnostic | To detect or confirm presence of a disease or condition of interest or to identify individuals with a subtype of the disease | To confirm an underlying α-synucleinopathy; to distinguish subtype of α-synucleinopathy (ie, Parkinson’s disease, dementia with Lewy bodies, multiple system atrophy) |
| Prognostic | To identify likelihood of a clinical event, disease recurrence, or progression in patients who have the disease or medical condition of interest | To predict rate of phenoconversion; to predict disease severity |
| Monitoring or therapy-responsive* | To monitor progression of disease or show that a biological response has occurred in an individual who has been exposed to a medical product or an environmental agent | To monitor the progression of neurodegeneration; to detect the eventual effect of drug treatment (extent of neuroprotection); to establish efficacy of disease-modifying therapies |
| Combined | Composite and multidimensional, through combination of multiple biomarkers, and, as such, better reflects biological systems than single biomarkers | To refine and enhance the diagnostic, prognostic, and monitoring capabilities of single biomarkers in isolated RBD |
Definitions in the second column adapted from Califf.2 RBD=rapid-eye-movement sleep behaviour disorder.
*
For simplicity, we have included biomarkers that hold promise as therapy-responsive markers in the monitoring category, as data are currently limited to longitudinal observational studies; when disease-modifying therapy trials are carried out, these monitoring biomarkers might also be considered as therapy-responsive biomarkers.