STORAGE OF SERUM OR WHOLE-BLOOD SAMPLES - EFFECTS OF TIME AND TEMPERATURE ON 22 SERUM ANALYTES

Information on the stability of serum analytes during storage of serum or whole blood samples is often incomplete and sometimes contradictor y. Using a widely available analyser (Hitachi 737/Boehringer), we ther efore determined the effects of storage time and temperature on the me asured concentrations of the following serum analytes: sodium, potassi um, calcium, chloride, inorganic phosphate, magnesium, creatinine, ure a, uric acid, bilirubin, cholesterol, HDL- and LDL-cholesterol, triacy lglycerols, creatine kinase, aspartate aminotransferase, alanine amino transferase, gamma-glutamyltransferase, alkaline phosphatase, alpha-am ylase, lactate dehydrogenase and cholinesterase. When separated serum was stored at + 9 degrees C for seven days, the mean changes in inorga nic phosphate and lactate dehydrogenase exceeded significantly (p < 0. 05 or 0.001, respectively) the maximum allowable inaccuracy according to the Guidelines of the German Federal Medical Council; all other qua ntities were sufficiently stable. In serum at room temperature, inorga nic phosphate, uric acid, HDL-cholesterol and triacylglycerols increas ed continuously, whereas bilirubin, LDL-cholesterol, creatine kinase a nd aspartate aminotransferase decreased more than the guidelines permi t during the storage period (p < 0.05 for aspartate aminotransferase, p < 0.001 for the other analytes mentioned). In whole blood stored for 7 days at + 9 degrees C, only the following serum analytes satisfied the stability requirements of the guidelines: calcium, urea, cholester ol, HDL-cholesterol, LDL-cholesterol, triacylglycerols, creatine kinas e, gamma-glutamyltransferase and cholinesterase. When stored at room t emperature, only sodium, uric acid, bilirubin, cholesterol, triacylgly cerols, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, alpha-amylase and cholinesterase were still stable after 3 days. The data collected show that all quantities examined are suff iciently stable for four days in separated serum stored at + 9 degrees C.