Assessment of thiamine status in humans

Thiamine (vitamin B1) is an essential nutrient with established adverse health consequences associated with acute deficiency. Emerging evidence also suggests long-term neurocognitive deficits due to sub-clinical deficiency in early life, and there is a growing appreciation of a potential role for thiamine in Alzheimer's disease. Therefore, the assessment of thiamine biomarkers, particularly in large, population-based studies, is critical to grasp the true scope of this public health problem. The most reliable biomarkers of thiamine status are whole blood concentrations of thiamine diphosphate (ThDP) measured by high performance liquid chromatography (HPLC) with fluorescence detection or liquid chromatography tandem mass spectrometry (LC-MS/MS), and the functional assay of transketolase activity (erythrocyte transketolase activity coefficient, ETKAC). Plasma thiamine reflects recent intake, and is not a useful biomarker of thiamine status. This manuscript describes the different biomarkers and methods of assessment, their advantages and disadvantages, and related cutoffs for deficiency. A table of 'performance characteristics' is provided to guide users on the quality and performance characteristics of each assay, and practicalities related to their cost, resource requirement, and maintenance. Provision of these insights will help inform decisions about inclusion of thiamine analysis in future work to better understand the extent of global thiamine deficiency.