The automation of sediment urinalysis using a new urine flow cytometer (UF-100™)

The UF-100(TM) analyser is a fully automated instrument that stains the DNA and the membranes of the formed elements in native urine. The sample then passes as a laminar flow through a laser beam and light scattering, fluorescence and impedance are measured. The main purpose of the present work was to assess the analytical performance and the accuracy of the measurements of the UF-100(TM) analyser. No carryover was observed, while the linearity was higher then the upper limit (40000 total particles mu l(-1)) suggested by the manufacturer. The within-run imprecision was low, ranging from 17.7% to 2.4% and was up to threefold better than manual microscopy. Comparison of results obtained by sediment microscopy (performed according to National Committee for Clinical Laboratory Standards (NCCLS) recommendations) and by the UF-100(TM) analyser showed a linear correlation with r = 0.833 for erythrocytes, r = 0.934 for leukocytes, r = 0.880 for epithelial cells and r = 0.40 for casts. To evaluate the reliability of the UF-100(TM) analyser in detecting bacteria we compared the results with the microbial culture (n = 608). Using a cut-off value of bacterial count above 1800 mu l(-1) and at leukocyte count above 45 mu l(-1), the analyser detected positive cultures with a sensitivity of 87% and a specificity of 80%. In conclusion, the UF-100(TM) analyser can improve the work flow, increasing the output of urinalysis by reducing the number of specimens submitted for microscopy. Also the method provides reliable information for the identification of urinary tract inflammation and bacterial infection.