Abstract Background The accuracy of urinalysis relies on proper sample handling, including collection, transport, and storage. Delays, inadequate temperature control, and lack of preservatives can compromise test quality. The VACUETTE® Urine STB Tube (Greiner Bio-One, Austria) is a sterile, pierceable, evacuated PET urine collection tube with a spray-dried stabilizer offering improved tube performance. This multicentric prospective study aimed to evaluate the analyte stability and precision performance of the Urine STB Tube for urine biochemistry, test strip, and particle analysis. Methods The study took place between May and December 2024 at Cerba HealthCare Belgium laboratory and Ghent University Hospital in Belgium, using 411 anonymized leftover urine samples from two sites. These samples were analyzed for urinary creatinine, urea, uric acid, total protein, albumin, calcium, potassium, and chloride (Roche Cobas c702). Test strip analysis (Roche Cobas U601) and particle counts (erythrocytes, leukocytes, etc.) using automated microscopy (Roche U701) and fluorescence flow cytometry (FFC) (Sysmex UF-5000) were performed. The stability of analytes was assessed by comparing initial results (T0) with measurements taken at 4h, 8h, 24h, 48h, and 72h at room temperature. Bias between T0 and subsequent time points was acceptable if below the Total Change Limit (TCL). For the semiquantitative test strip and particles count analysis, a change of no more than one level in 95% of the samples was deemed acceptable, while for qualitative parameters, 95% had to remain consistent (positive or negative) compared with the T0 results. Analytical performance was evaluated by comparing imprecision for urine biochemistry, test strips, and particle counts between the STB tube and BD Vacutainer® Urinalysis Preservative Plus (UPT) Urine Tube. Coefficients of variation (CV) with 95% confidence intervals (CI) were compared. Imprecision was acceptable if the 95% CI lower bound of CV was = 1, otherwise compared with Acceptable Change Limit (ACL) and TCL. The same criteria from the stability study were applied for test strips and particle counts. Results All tested quantitative parameters in samples collected in STB tubes were stable at room temperature up to 72h. Further, all tested particle counts using both automated microscopy and FFC were stable at room temperature up to 72h, except for crystals, which were stable up to 8h when using the microscopy method. Additionally, stability was confirmed for all test strip parameters up to 72h, except for blood which was stable for 24h. Both STB and UPT tubes met the defined acceptance criteria for imprecision within tubes, between tubes and across different lots for all examined parameters. Conclusion The VACUETTE® Urine STB Tube provides excellent analyte stability for up to 72h and robust precision performance for urine biochemistry, test strip, and particle analysis. Blood on test strips and crystals in automated microscopy, were less stable (24h and 8h, respectively). Whereas blood test strip assay was most probably affected by the rapid loss of hemoglobin’s pseudoperoxidase activity over time, due to its sensitivity to various preservatives, the low stability of crystals warrants further investigation, as this instability was observed only in automated microscopy and not in FFC.
Šimundić et al. (Wed,) studied this question.
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