Transportation and handling of blood samples prior to ammonia measurement in the real life of a large university hospital

Background: Hyperammonemia is neurotoxic and as such can be a medical emergency. Preanalytical factors greatly influence the blood ammonia concentration results. Aims and methods: Ammonia concentrations measured in the real life setting of a large hospital after pneumatic transport of blood samples and various time periods before centrifugation were compared to those based on the indications of the reagent manufacturer. In the same routine context, the effects of waiting times of centrifuged samples or after plasma storage at −20 °C and −80 °C were determined. Results: Despite the pneumatic transport, the lead times for sample arrival to the lab were even longer than those recommended for their complete handling until ammonia assay. Ammonia concentration results were not affected by the pneumatic transport of blood samples and by waiting times up to a maximum of 1.75 h before their centrifugation and 1 h after centrifugation. Ammonia stability was superior when plasma was stored at −80 °C. Conclusion: Pneumatic transport and sample handling in the routine practice of our lab do not affect ammonia concentration results provided that waiting times are limited to 1.75 h before and 1 h after centrifugation and samples are kept cold. Otherwise, it is better to freeze plasma at −80 °C.