A-060 Assessing Glucose Stability: A Comparison of Citrate/NaF, NaF, and Gel Separator Vacuum Tubes in Routine Medical Laboratory Practice

Abstract Background In cases where a glycolysis inhibitor is not utilized, blood cells in vitro can consume glucose. Although current guidelines suggest using citrate-buffered inhibitors or ice-water slurry to mitigate this, practical and financial constraints often hinder adherence to these recommendations. Our objective was to evaluate the difference in glucose concentration in our routine sample management by employing Citrate buffered/NaF, NaF, and Gel Barrier tubes. Methods In this study, we utilized Greiner FCmix citrate-buffered NaF and EDTA tubes (3 mL), Becton Dickinson NaF and EDTA tubes (4 mL), and Becton Dickinson SSTII Gel Barrier tubes (5 mL). Following venipuncture, the tubes were transferred to the laboratory and centrifuged within 30 minutes. Glucose levels of 46 patients' samples were measured using a Cobas 6000 system (c501) employing the Glucose Hexokinase method, which exhibits an intermediate coefficient of variation (CV) of approximately 1.5% and no significant bias, as confirmed by monitoring with Biorad EQAS. Results The mean plasma glucose difference between Citrate-buffered tubes and NaF tube samples was 2.8 mg/dL with a 95% confidence interval (CI) ranging from 2.2 to 3.4 mg/dL (Mean: 0.16 mmol/L; CI: 0.12 - 0.19 mmol/L). The difference in paired samples of NaF plasma and Gel Barrier tubes serum glucose was 3.2 mg/dL with a CI of 2.5 - 3.9 mg/dL (Mean: 0.18 mmol/L; CI: 0.14 - 0.22 mmol/L). Lastly, the mean difference in Citrate-buffered plasma and serum Gel barrier tubes for 46 paired samples was 6.0 mg/dL with a CI of 5.2 - 6.7 mg/dL (Mean: 0.33 mmol/L; CI: 0.29 - 0.37 mmol/L). Conclusions Following guidelines, Citrate-buffered/NaF tubes demonstrate efficacy as glucose stabilizers. When compared to NaF tubes alone within a 30-minute timeframe, the mean difference between the two types of tubes was 2.8 mg/dL. Although NaF tubes are no longer recommended for glucose testing in plasma, they still outperform gel barrier serum tubes by 3.2 mg/dL. Furthermore, compared to citrate/NaF Plasma, serum glucose levels were on average 6.0 mg/dL lower. The preanalytical sample stage poses a significant obstacle to its reliable use for diagnostic or monitoring purposes. Laboratories should consider transitioning to Citrate/NaF tubes, or employ mathematical corrections if utilizing gel separator tubes for glucose testing in their established preanalytical process.