Plasma reference interval of Trimethylamine-N-oxide in healthy adults: A multicenter study using Trimethylamine-N-oxide assay kit for analysis and validation.

Background: Trimethylamine-N-oxide (TMAO) is a potential cardiovascular biomarker in Chinese people without a defined plasma reference range. Its clinical application is restricted due to incomplete knowledge of pre-analytical factors' impact on measurement.

Methods: Assess the effects of standard anticoagulants and pre-analytical factors on TMAO test outcomes to determine optimal conditions. Plasma TMAO levels in 649 healthy Chinese individuals were analyzed using a non-parametric approach to set a 95% reference interval. Examine how age, gender, region, and BMI affect TMAO levels and their correlation with clinical metrics like blood pressure, glucose, lipemia, and liver-kidney function.

Results: Anticoagulants had minimal effect on TMAO assay results. TMAO concentrations remain stable during sample storage at 4 °C for 24 h, 25 °C for 12 h, or 35 °C for six h before centrifugation -prolonged storage at 25 °C or 35 °C results in changes below the acceptable limit. The 95 % reference interval for plasma TMAO is 5.72 µM, with a median of 1.70 µM and an interquartile range of 1.09-2.53 µM. Age, sex, region, and BMI do not affect TMAO levels. SBP, FPG, TC, and BUN positively correlate, while HDL-C, ALT, AST, and TBIL negatively correlate with TMAO.

Conclusions: This guides for selecting blood collection tubes for TMAO detection and optimal pre- centrifugation storage conditions. We set a 95% reference interval for plasma TMAO in healthy adults in China and examined the correlation between TMAO levels and demographic and biochemical markers.