Table 3.

Analytical requirements for thiamine biomarkers

	ThDP	ETKAC
Assay type	Direct measurement	Indirect/functional assay
Analytical instrument	HPLC or LC–MS/MS	UV spectrophotometer
Specimen type	Whole blood or washed erythrocytes	Washed erythrocytes
Collection tube	Heparin or EDTA	Heparin or EDTA
Sample processing	3× saline wash to purify erythrocytes or hemolyzed whole blood	3× saline wash to purify erythrocytes
Minimum volume	For HPLC: 300 μL For LC–MS/MS: 150 μL	30 μL
Storage	Room temperature for a few hours, store at –20 °C for a few months, –70 °C for several months/years	Room temperature for a few hours, store at –20 °C for a few weeks, –70 °C for several months/years
Shipping	Dry ice	Dry ice

ThDP, thiamine diphosphate; ETKAC, erythrocyte transketolase activation coefficient; HPLC, high‐performance liquid chromatography; LC–MS/MS, liquid chromatography coupled to tandem mass spectrometry; EDTA, ethylenediaminetetraacetic acid.