Urine transfer devices may impact urinary particle results: a pre-analytical study

Objectives: Well-standardized procedures in the pre-analytical phase of urine diagnostics is of utmost importance to obtain reliable results. We investigated the effect of different urine collection methods and the associated urine transfer tubes on urine test strip and particle results. Methods: In total, 146 selected urine samples were subdivided into three different collection containers and subsequently transferred into its accompanying transfer tube ( BD, Greiner, Sarstedt vacuum and Sarstedt aspiration). As reference, the original urine sample was directly measured on the analyser. Both chemical test strip analysis (Sysmex UC-3500) and fluorescence flow cytometry particle analysis (Sysmex UF-5000) were performed on all samples. Results: No statistically significant differences in test strip results were found between the studied transfer methods. On the contrary, transfer of urine samples to the secondary tubes affected their particle counts. Clinically significant reductions in counts of renal tubular epithelial cells and hyaline casts were observed using the BD and Greiner transfer tubes and in counts of pathological casts using the BD, Greiner and Sarstedt vacuum tubes. Conclusions: The results of this study indicate that the use of urine transfer tubes may impact counts of fragile urine particles. Clinical laboratories need to be aware about the variation that urine collection methods can induce on urine particle counts.