Evaluation of Refrigerated Stability of 15 Analytes in Lithium Heparin Gel Primary Tubes

Abstract

To determine the stability of 15 analytes when plasma specimens are placed in refrigerated storage to enable add-on testing. Blood samples were obtained from 40 volunteer outpatients and collected in plasma separator tubes. The tubes were spun to obtain platelet-poor plasma, which was analyzed for a comprehensive metabolic panel at 1 hour after collection and placed into refrigerated storage for subsequent analyses. Repeat analyses occurred at 8, 16, 24, 48, and 72 hours after collection. Subsets of 5 patient samples were aliquoted into secondary tubes after initial analysis and reanalyzed at the same time points. Stability was defined as no change within calculated acceptable allowable limits. After refrigerated storage in the primary tube, most analytes were stable for the first 24 hours. The analytes that showed clinically significant changes after storage in the primary tube were glucose, potassium, CO2, and aspartate transaminase (AST). All analytes from the aliquot tubes remained stable for the duration of the study. The duration of stability for most analytes we tested was at least 24 hours in the gel tube or the aliquot. Analytes are stable for longer periods of time when stored in aliquot tubes, remixed, and re-spun before analysis.