The effectiveness of BD Vacutainer® Plus Urinalysis Preservative Tubes in preservation of urine for chemical strip analysis and particle counting

INTRODUCTION: The aim of this study was to evaluate the stability of urine collected in preservative tubes for chemistry strip analyses and particle counting to determine whether the transport of urine samples with all of their constituents is possible. MATERIALS AND METHODS: 275 pathologic urine specimens were included. Each urine sample was evaluated after 4, 8, 12, 24, and 48 hours of storage in BD Vacutainer® Plus Urinalysis Preservative (BD UAP) tubes and compared with refrigeration at 4 °C. All analyses were peformed on H-800 and FUS-200 automatic modular urine analyzers (Dirui Industry, Changchun, China). The kappa coefficients (κ), false positive (FP) and false negative (FN) rates were evaluated. κ > 0.8 was accepted as good agreement. RESULTS: Haemoglobin (Hb), leucocyte esterase (LE), and protein (Pro) analyses should be performed within 4 hours, whereas glucose (Glc) was stable until the end of 48 hours in both storage conditions. Nitrite (Nit) was well preserved in BD UAP tubes for 24 hours but was stable only up to 8 hours at 4 °C. Bilirubin (Bil) had very high FN rates even at 4 hours in both conditions. The particle counting showed high FN rates for white blood cells (WBC) and red blood cells (RBC), whereas squamous epithelial cells (EC) were stable up to 8 hours in both conditions. CONCLUSIONS: Preanalytical requirements for both urine chemical strip analyses and particle counting in a unique sample were not met in either condition. Thus, the transfer of urine samples for centralization of urinalysis is not yet feasible.