A Framework for the development of biomarkers, as in Abi-Dargham and Horga. Nat Med 2016. In a recent review (Abi-Dargham et al. World Psychiatry 2023), the FSA was highlighted as one of the most advanced biomarkers in schizophrenia, at the stage of external validation. B Summary of the development and leave-one-site-out cross-validation of the FSA as a diagnostic biomarker, as in Li et al. Nat Med 2020. C The current work consists in calculating FSA scores using the same method as in the original research to replicate the classification of diagnosis and correlation with treatment response by the FSA, to corroborate external validation.