An evaluation of a modified erythrocyte transketolase assay for assessing thiamine nutritional adequacy.

Transketolase (TK) activity was assessed by incubating hemolyzed whole blood with ribose-5-phosphate both in the presence (TKsat.) and in the absence (TK) of thiamine pyrophosphate (TPP). The amount of pentoses utilized between 5 and 60 min after the start of the incubation was taken as a measure of the TK activity. The TPP effect was expressed at (TKsat. - TK)/TK x 100. The coefficient of variation for the TPP effect determination was 9.6% within the TPP effect range from 6 to 22%. Within the TPP effect range from 24 to 46%, the coefficient of variation was 8.7%. The mean TPP effect as measured in a group of healthy individuals amounted to 13.5%, with a range from 8.3 to 18.5%. In a group of obese women submitted to an energy-restricted diet, the TPP effect ranged from 12.7 to 30%. In patients suffering from Wernicke's encephalopathy, the TPP effect varied from 28 to 67%.