Information on the stability of serum analytes during storage of serum or whole blood samples is often incomplete and sometimes contradictory. Using a widely available analyser (Hitachi 737/Boehringer), we therefore determined the effects of storage time and temperature on the measured concentrations of the following serum analytes: sodium, potassium, calcium, chloride, inorganic phosphate, magnesium, creatinine, urea, uric acid, bilirubin, cholesterol, HDL-and LDL-cholesterol, triacylglycerols, creatine kinase, aspartate aminotransferase, alanine aminotransferase, -glutamyltransferase, alkaline phosphatase, -amylase, lactate dehydrogenase and cholinesterase.When separated serum was stored at + 9 °C for seven days, the mean changes in inorganic 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 quantities were sufficiently stable.In serum at room temperature, inorganic phosphate, uric acid, HDL-cholesterol and triacylglycerols increased continuously, whereas bilirubin, LDL-cholesterol, creatine kinase and aspartate aminotransferase decreased more than the guidelines permit 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 °C, only the following serum analytes satisfied the stability requirements of the guidelines: calcium, urea, cholesterol, HDL-cholesterol, LDL-cholesterol, triacylglycerols, creatine kinase, -glutamyltransferase and cholinesterase. When stored at room temperature, only sodium, uric acid, bilirubin, cholesterol, triacylglycerols, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, -amylase and cholinesterase were still stable after 3 days.The data collected show that all quantities examined are sufficiently stable for four days in separated serum stored at + 9 °C.

There is no comprehensive study on the stability of coagulation analytes in plasma. We therefore determined the influence of storage time and temperature on prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, factors V and VIII, antithrombin III, protein C and S in plasma from 20 healthy subjects and 20 patients receiving heparin therapy. The stability in plasma, defined as the period during which there was a change of less than 10% from the initial value, was 8 hours for activated partial thromboplastin time, 24 hours for prothrombin time, 48 hours for factor V and 7 days for thrombin time, fibrinogen, protein C and antithrombin III in healthy subjects at 6 degrees C. Factor VIII and protein S showed 19 and 12 % reduction in activity, respectively, after 8 hours. In volunteers not treated with heparin therapy, activated partial thromboplastin time was stable for 8 hours; prothrombin time for 48 hours; and thrombin time, fibrinogen and antithrombin III for 7 days with sample storage at room temperature. Factor VIII showed a decrease of 18 % after 8 hours. For patients receiving heparin therapy, the stability of the analytes in plasma stored at 6 degrees C was 8 hours for thrombin time, 24 hours for prothrombin time and activated partial thromboplastin time and 7 days for fibrinogen and antithrombin III. Factors V and VIII showed a decrease of 13 % and 20 % respectively after 8 hours. When the plasma of these patients was stored at room temperature, factor V was stable for 8 hours, and prothrombin time for 24 hours, whereas fibrinogen and antithrombin III remained unchanged for 7 days. Activated partial thromboplastin time showed an increase of 13 %, thrombin time a fall of 16 %, and factor VIII a decrease of 18 % after 8 hours.