Analytical validity asks: does the assay measure what it claims? For iFRETLoading..., this means demonstrating that FRET efficiency accurately reflects protein-protein proximity, with appropriate precision, reproducibility, and robustness.
Clinical validity asks: does the biomarker correlate with outcomes? The PD-1/PD-L1 iFRET studies demonstrating p=0.05 survival correlation (vs. p=0.87 for expression) establish clinical validity.
clinical utilityLoading... asks: do biomarker-guided decisions improve outcomes? This requires prospective interventional trials showing that using the biomarker leads to better patient outcomes than standard care.