Exploratory biomarkers: Analytical approaches and their implications

While biomarker discovery is receiving increased attention in both drug and chemical safety assessment, a critical step is transitioning a biomarker from an experimental observation to a useful assay is that of analytical validation. This is particularly relevant as one moves from biomarker discovery using an omics platform to exploratory use as implemented in a more focused platform. Large scale discovery platforms for transcriptomics, such as microarrays, have unique analytical considerations, different from that of more focused platforms, such as qRT-PCR. Likewise, mass spectrometry based screens of the proteome have different analytical challenges as compared to focused ELISA assays. Metabolomics experiments also require attention to analytical validation, with different considerations for quantitative or semi-quantitative assays. And while guidelines for analytical validation are still evolving, general principles certainly apply, with a solid body of literature that should be consulted by the biomarker scientist before deeming an assay as worthy of more widespread use.