The Automation of Sediment Urinalysis Using a New Urine Flow Cytometer (UF-100™)

Abstract

The UF-100 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 analyser. No carryover was observed, while the linearity was higher then the upper limit (40000 total particles microl(-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 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 analyser in detecting bacteria we compared the results with the microbial culture (n = 608). Using a cut-off value of bacterial count above 1800 degrees l(-1) and at leukocyte count above 45 microl(-1), the analyser detected positive cultures with a sensitivity of 87 % and a specificity of 80 %. In conclusion, the UF-100 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.

Automated urinalysis: first experiences and a comparison between the Iris iQ200 urine microscopy system, the Sysmex UF-100 flow cytometer and manual microscopic particle counting

“…Therefore, urine samples from patients suspected of suffering from nephritis must be analyzed by manual microscopy (26). Our results are consistent with findings of other studies showing that the UF-100 has greater deficits when analyzing samples with high numbers of crystals, yeast and sperm cells known to overlap with the erythrocyte gate in the scattergram (27,30,33).…”

“…We observed overestimation of bacteriuria by the UF-100, probably due to misidentification of amorphous debris or other small particles such as bacteria. This poor specificity of the bacterial count by the UF-100 was reported previously (30).…”

“…Automation may be helpful in solving these problems and improves the accuracy and precision of urine sediment analysis. Several studies compared automated image-based analysis systems and/or flow cytometer-based systems with manual microscopy (6,(19)(20)(21)(22)(23)(24)(25)(26)(27), and most recognized the accuracy and precision of automated systems (28)(29)(30)(31)(32), as well as their feasibility as routine screening tools (8,10,17,18,33,34).…”

“…For this study we did not use this advantage so that results would be comparable with the conventional microscopic technique. The main error-prone steps such as centrifugation and manual preparation are omitted and therefore sample analysis is completed in a very short turnaround time (9,30); the hands-on time, including picture or scattergram interpretation, is less than 30 s on average. In our laboratory, which performs approximately 25,000 urinalyses per year, this strategy reduced the workload by approximately 30%.…”

“…The UF-100, however, yields more false-positive results for leukocytes compared to the iQ200. In particular, naked epithelial cells or transitional cells can be misclassified as leukocytes (27,30). The total accuracy rates for the iQ200 tended to be higher than those of the UF-100.…”