Effect of Storage Time and Temperature on the Stability of Serum Analytes

Abstract Background  Determining the pattern of analytes stability with regard to time duration and temperature of storage is compulsory to maintain the precision and accuracy of measurements. Hence, this study aimed to assess the stability of 19 common serum analytes in relation to time length and storage temperatures. Methods  Serum specimens from healthy adult volunteers were obtained, transferred into a single BD falcon tube, gently mixed. About 300µL of serum was taken and immediately analyzed to determine the concentration of 19 common serum analytes to use the results as a baseline value for the characterization of analytes stability. Then the serum aliquoted into 24 sterilized Nunc tubes (300µL in each) and six aliquots were stored in each storage temperature like 17°C, 2-8 °C, -20°C and -41°C. Then the aliquots analyzed in parallel on days 5, 10, 15, 20, 25, and 30. Results  At 17°C, amylase (AMY), Urea (URE), total protein (TP), Creatinine (CREA) and Glucose (GLU) were stable until day 25 with <3% change of the starting value, while the rest analytes were very unstable throughout 30 days. At 2-8 °C, alkaline phosphatase (ALP), creatine phosphatase (CK-T), cholesterol (TC), AMY, LDL-cholesterol (LDL-c), TP, and GLU were stable until day 30 with ≤4% change of the initial value. At -20°C and -410C, AMY, pancreatic amylase (AM-P), LDH, TC, triglyceride (TG), GLU, PHO, and TP were stable for 30 days with ≤3.1% change from a baseline value. Novel findings: the following tests were stable at 170C for 25 days with the maximum change of urea <2%, glucose <3%, protein total <1% and amylase 0.0% Conclusion  This study tried to evaluate the stability of serum biochemicals at four different storage temperatures concurrently. Each serum biochemical has inimitable stability characteristics in diverse storage temperatures. Therefore, clinical laboratories should store specimens using appropriate temperatures as soon as possible by considering the length of storage time. Keywords: Serum, Biochemical analytes, Stability, Storage temperature