Assay values for thiamine or thiamine phosphate esters in whole blood do not depend on the anticoagulant used

We compared the whole blood, plasma, and erythrocyte (red blood cell (RBC)) concentrations of thiamine and thiamine phosphate esters in the presence of heparin or EDTA as anticoagulants. Three blood specimens were collected from each of 24 healthy volunteers into evacuated collection tubes containing the following anticoagulants: heparin, Na2EDTA, or K2EDTA. The concentrations of nonphosphorylated free thiamine (T), thiamine monophosphate (TMP), thiamine diphosphate (TDP), and thiamine triphosphate (TTP) were determined by the NH2-column HPLC method. The anticoagulant used had no effect on the concentrations obtained in whole blood and plasma of thiamine or any of the above thiamine compounds (P > 0.05). RBCs were isolated by centrifugation and washed with isotonic saline, and the cell counts of the washed cells were adjusted to their whole blood values. In the washed RBCs with any anticoagulant, the concentrations of T, TMP, and TDP expressed either as nmol/L of whole blood or a ratio to hemoglobin were significantly lower (P < 0.05) than those in whole blood.