biomarker validation clinical validation https://pubmed.ncbi.nlm.nih.gov/33545385/ https://pubmed.ncbi.nlm.nih.gov/32541893/ Clinical validation aims to establish an association between the biomarker and the endpoint of interest and to demonstrate the usefulness of the biomarker. Clinical validation relies on external validation and can be done by retrospective use of clinical trial data or by prospective clinical trials. Retrospective use of clinical trial data is a form of external clinical validation where the biomarker evaluation is not part of the original study design.