Effect of Preanalytical Techniques and Variables on Plasma Ammonia Estimation

Ammonia concentration may increase or decrease due to the mishandling of blood specimens. Among the factors that affect ammonia concentration, blood collection, type of anticoagulant, centrifugation forces, atmosphere and storage temperature. We focused on the effect of centrifugation forces, type of anti coagulant and the complete filling of the blood collection tube. Ten male healthy volunteers, each with replicate specimens were used in this study. Results show that the use of non hemolysed , non clotted specimen and prompt centrifugation (1500 X g; 15 minutes) apparently were important in avoiding such increase in Ammonia concentration. It was also found that EDTA - Plasma is preferred over the other anticoagulated specimen for ammonia determination. Complete filling of the specimen tube was found to have no significant effect on ammonia concentration. We concluded that the procedure used for collection and storage of specimens for ammonia determination should be standardized and strictly observed