Changes in erythrocyte transketolase activity and the thiamine pyrophosphate effect during storage of blood

Whole blood and washed erythrocytes from nutritionally normal and abnormal elderly patients were stored at room temperature, 4 degrees C and -20 degrees C for up to 14 days. In both groups, and under all storage conditions, the erythrocyte transketolase (ETK) activity and the thiamine pyrophosphate (TPP) effect decreased with time of storage. The ETK activity for specimens stored at -20 degrees C decreased significantly by day 14 (P less than 0.05). The TPP effect in specimens stored at -20 degrees C decreased significantly in the nutritionally abnormal group at 4 days (P less than 0.05) and in the nutritionally normal group by day 14 (P less than 0.05). These significant changes in ETK activity and TPP effect with storage can lead to misleading interpretation of thiamine nutritional status.