Does an optimal TMAO result rule out gut-derived cardiometabolic risk?

A circulating trimethylamine N-oxide (TMAO) measurement may be biologically informative in selected settings, but an “optimal” result does not establish that gut-derived cardiometabolic risk is absent.

Clinical interpretation

• Prospective evidence links higher TMAO concentrations with adverse outcomes; in MESA, participants in the highest versus lowest TMAO quintile had about 32% higher incident ASCVD risk after multivariable adjustment.
• This association does not yield a validated low-TMAO cutoff, sensitivity, or population-wide negative predictive value that can rule out future cardiovascular or cardiometabolic risk.
• The reported 98% negative predictive value at 478 ng/mL arose in a small cohort following acute myocardial infarction. It should not be extrapolated to an asymptomatic 52-year-old man or primary-prevention use.

Biological and measurement context

• Kidney function is a major determinant of fasting circulating TMAO because renal clearance materially affects its concentration. Renal injury and TMAO may also have bidirectional relationships, complicating causal interpretation.
• A single result also reflects recent diet (including seafood and red meat), microbial trimethylamine production, fasting status, medications, assay methods, and renal function. Thus, a low value indicates only that marked circulating elevation was not detected under those conditions—not that relevant microbial, metabolic, or vascular processes are absent.

Clinical implications

• TMAO has not demonstrated reliable incremental prognostic discrimination or outcome improvement beyond established cardiovascular assessment, and routine testing is not recommended in established cardiovascular guidelines.
• It should be treated, at most, as an adjunct in selected contexts rather than a replacement for validated cardiometabolic risk evaluation.

Bottom line

• An optimal TMAO result does not rule out a high-TMAO gut-derived cardiometabolic risk signal or future cardiovascular risk; standard validated risk assessment remains the appropriate basis for clinical decision-making.