known_biases: Patients undergoing elective diagnostic coronary angiography at the Cleveland Clinic (Hazen lab), with TMAO/choline metabolites assayed in one lab that holds patent/commercial interests in TMAO diagnostics — a sick, referral-selected, high-baseline-risk population (not general-population), one analytic/assay pipeline, and a COI-laden reporting actor, so every Hazen-lab TMAO-to-events association resting on this biobank is correlated rather than independent.