Routine Workflow for Use of Urine Strips and Urine Flow Cytometer UF-100 in the Hospital Laboratory,1

Abstract

None of the methods currently available for evaluating hematuria and leukocyturia is perfect. Urinalysis by test strip combined with automated particle counting is an attractive approach that may identify false-negative results of both techniques. We wished to evaluate the possibility that microscopic evaluation of urine samples could be substantially reduced by this approach. The fully automated urine flow cytometer UF-100 classifies urinary particles on the basis of their light scattering, fluorescence, and impedance properties. The instrument counts erythrocytes, leukocytes, bacteria, epithelial cells, and casts and flags the presence of pathological casts, small round cells (SRCs), yeast-like cells, crystals, and spermatozoa. The instrument is intended to replace, to an extent, routine urine microscopy. The operating principles of the UF-100 (1); its precision, accuracy, and analytical sensitivity (2); and its potential for differentiation between renal and postrenal hematuria (3) have been published previously (4). The precision of particle counting in microscope chambers is poorer than counting by flow cytometry (5). The analysis of urine samples by UF-100 and the test strip analyzer Clinitek Atlas showed discordant results in a small but not negligible number of cases. This result has also been described by Ben-Ezra et al. (4). We therefore rechecked the false results in erythrocyte and leukocyte counts by examining discrepant results from both instruments by microscopic evaluation and evaluated a workflow for the routine urine analysis using the combination of UF-100 and Clinitek Atlas. We analyzed 288 mainly pathological urine specimens by both test strip analyzer (Clinitek Atlas; Bayer Diagnostics) and UF-100 (Sysmex). The samples were examined within 3 h of arriving at the laboratory; no preservatives were used. We additionally reviewed 261 by microscopy. The ranking system …