The effects of pre-analysis sample handling on human plasma amino acid concentrations

The accurate and reliable quantification of amino acid concentrations in human plasma is important for the investigation of a number of diseases. However, few systematic studies investigating the changes in amino acid concentrations related to blood collection and storage conditions have been completed. Blood samples were collected with EDTA-Na2 from 3 healthy volunteers and subjected to a number of different treatments; hemolysis, temperature after blood collection, time from blood collection to cooling, the influence of platelets, long term storage conditions, and repeated freeze–thaw cycles. Changes in the concentrations of 22 amino acids were determined using an Amino Acid Analyzer. Of the conditions influencing sample stability between blood collection and amino acid analysis, hemolysis, temperature after blood collection, and long-term storage at −20°C affected the concentrations of 11 amino acids. Time from blood collection to cooling, platelet contamination and repeated freeze–thaw cycles altered the levels of 4 amino acids. We observed changes in amino acid concentrations relating to blood collection and storage conditions. If attention is paid to 4 key factors (hemolysis, temperature immediately following blood collection, time from collection to cooling, and long-term storage temperature) 19 amino acids can be reliably quantified. •We systematically evaluated the changes in human plasma amino acid concentrations.•Sample handling and storage conditions impacted on many amino acid concentrations.•If attention is paid to 4 key factors, 19 amino acids can be reliably quantified.