SUMMARY. Whole blood and washed erythrocytes from nutritionally normal and abnormal elderly patients were stored at room temperature, 4 c e and -20 c e 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 c e decreased significantly by day 14 (P<0·05). The TPP effect in specimens stored at -2OCe decreased significantly in the nutritionally abnormal group at 4 days (P<0·05) and in the nutritionally normal group by day 14 (P<0·05). These significant changes in ETK activity and TPP effect with storage can lead to misleading interpretation of thiamine nutritional status.Erythrocyte transketolase (ETK) assays are widely used to assay thiamine status indirectly. There is, however, no clear consensus on the stability of the enzyme under different storage conditions. Brin' reported that haemolysed specimens are stable for only a matter of hours at room temperature, 2-3 days at 4 believed, this could perhaps contribute to these variations.We investigated, therefore, possible changes in the saturated and unsaturated ETK activities and the TPP effect after storage at different temperatures. Method SUB1ECTSThe nutritional status of 22 elderly in-patients was assessed on the basis of their dietary history, weight and anthropometric measurements. Eleven were considered to be nutritionally normal, with a mean age of 74 (67-90) years whereas 11 were regarded to be nutritionally abnormal, with a mean age of 76 (6&-84) years. None of the subjects had any evidence of infection. SAMPLE PREPARATION AND STORAGETwenty millilitres of heparinised blood was centrifuged at 3000g for 5 min, following which the plasma and buffy coat were discarded. An equal volume of cold sodium chloride solution (140 mmoUL) was added to the erythrocytes and then centrifuged at 3000 g for 5 min; the supernatant was discarded and the washing procedure repeated twice.
A prospective study of thiamine status in patients with severe injuries (injury severity scores greater than 12) showed that they all developed signs of severe thiamine deficiency on the basis of transketolase activity, the standard biochemical test for thiamine deficiency. This occurred within the first week after their injuries despite routine enteral or parenteral feeding including vitamin supplements. This may be due to increased requirements secondary to increased metabolic activity or increased cellular losses. An increased awareness of thiamine requirements and metabolism is essential to avoid the appearance of deficiency syndromes.
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