STABILITY OF SELECTED BIOCHEMICAL ANALYTES IN STORED SERUM SPECIMEN AT KERICHO COUNTY REFERRAL HOSPITAL, KENYA

Abstract

Accurate and reliable medical laboratory test results are essential for correct patient diagnosis and management. Pre-analytical variables, including samples storage, can adversely affect the reliability of medical laboratory results. Add-on tests, alongside unprecedented delays in testing, require that serum samples are stored in a manner that maintain their integrity and optimally preserve the various analytes. To ensure accurate results from stored samples, the determination of the stability of the analytes under various environmental conditions and storage periods is important in informing acceptable sample handling and storage. This study aimed at evaluating the stability of selected biochemical analytes in relation to storage time, exposure of light and temperatures to determine the maximum storage period at which accurate and reliable results can still be obtained at the Kericho County Hospital laboratory. Samples drawn from twenty healthy volunteering adult participants, randomly picked from the local population, were processed and analysed at baseline, then set of aliquots was made into 16 sterilized tube and stored at 2- 8℃, -20℃ and other different environmental condition, expose light and other kept in the dark, in batches marked for analysis on the 7th, 14th, 21st and 28th days for aliquots refrigerated and frozen, for environmental condition was analysed at 2, 4, 8 and 24 hours. The data was coded and analysed on SPSS version 22. The statistical significance of the difference in the determined analyte concentrations in comparison to baseline levels was evaluated using student paired T-test and Wilcoxon rank test. From the findings, alkaline phosphate, creatinine, and aspartate aminotransferase were found to be stable up to 28 days in the refrigerated and frozen, with mean percentage differences less than calculated reference change value of 16.48%, 35.97% and 42.25% respectively. Sodium, total and direct bilirubin, were however unstable, as their mean percentage difference was more than the calculated reference change value of 2.16%, 0.657% and 1.14%. Urea and glucose showed stability at 2-8℃ for up to the 14th day, while potassium and chloride were only stable in refrigerated serum up to the 7th day. Freezing improved the stability of all the analytes except bilirubin, alanine aminotransferese and sodium. Chloride, creatinine, glucose, potassium, sodium, urea, alkaline phosphates, alanine aminotransferese and aspartate aminotranferese were stable up to 24 hrs when serum sample left at room temperature as their calculated reference change value were 4.54%, 35.97%, 13.14%, 10.89%, 2.16%, 32.15%, 16.48%, 42.25% and 42.52% were less than mean percentage difference respectively only total and direct bilirubin were only stable for 4hrs and 2 hrs. respectively as their mean percentage difference of 0.48 and 0 were less than calculated RCV of 0.675 and 1.14. When serum samples were exposed to light and other aliquots kept in the dark, only total and direct bilirubin were unstable with reference change value of 1.14% and 0.675% respectively. Total bilirubin was only stable for 4 hours with calculated reference change value of -0.48% which is less than reference change value when serum samples were exposed to light but kept in the dark it was stable for 8hrs. This study recommends immediate analysis of serum for sodium, bilirubin, and alanine aminotransferese , which should never be part of add-on tests, and freezing of the samples when analysis is delayed for the other analytes. The findings of this study will help policy makers to make good decisions on health sectors on which laboratory equipment to procure in terms of refrigerators and freezers.