Abstract Background While laboratories usually prefer either serum or plasma as the sample matrix for routine chemistry tests, it is well known that the stability of individual analytes can vary substantially between these matrices. This study compares the stability of 12 clinical chemistry parameters (ALT, complement C3, calcium, cortisol, chloride, HDL, creatinine, sodium, TSH, total bilirubin, total protein, vitamin B12) in VACUETTE® CAT Serum Separator Tubes and VACUETTE® LH Lithium Heparin Separator Tubes. Both tubes are available in the US market. Methods The study was conducted at the Greiner Bio-One GmbH testing laboratory in Kremsmünster, Austria, in April 2023. Approval of the Ethics Committee of the Faculty of Medicine at the Johannes Kepler University Linz, Austria, was obtained. Samples were collected from 20 presumably healthy donors, who provided informed consent, in VACUETTE® CAT Serum Separator Tubes and VACUETTE® LH Lithium Heparin Separator Tubes. All tubes were stored upright for 30 min before centrifugation and were analyzed within 30 min after centrifugation. After initial analysis, tubes were stored capped at room temperature and protected from light exposure and measurement was repeated after 24 h. Tubes were capped and stored refrigerated (4 – 8 °C) for further 24 h but were equilibrated to room temperature 30 min before the measurement. All analyses were performed on the Beckman Coulter AU680 instrument. The Total Change Limit (TCL) was defined as maximum permissible difference. To calculate the TCL, the formula TCL = (2.77 x CVA)² + (0.5 x CVI)²½ was applied, where CVA represents the analytical imprecision and CVI represents the intra-individual biological variability. If the mean percent difference including the 95% confidence interval (CI) exceeded the TCL, the analyte was not considered stable. Results The overall mean percent difference including the 95% CI was within the TCL at both time points (24 h and 48 h) for all 12 analytes in VACUETTE® LH Lithium Heparin Separator Tubes. In VACUETTE® CAT Serum Separator Tubes the overall mean bias including the 95% CI was within the TCL at both time points (24 h and 48 h) for all analytes except for complement C3, where the TCL was exceeded at the time points 24 h and 48 h. Conclusion 11 out of 12 parameters showed equal stability in both blood collection tube types. Only for complement C3 a difference in stability was observed, with 48 h post-centrifugation stability in VACUETTE® LH Lithium Heparin Separator Tubes, whereas no stability was observed in VACUETTE® CAT Serum Separator Tubes at both investigated time points (24 h and 48 h).
Šimundić et al. (Wed,) studied this question.