Urine particle evaluation: a comparison between the UF-1000i and quantitative microscopy.

BACKGROUND: The study of urine particles plays a key role in the diagnosis of kidney diseases. In this study, the authors evaluated the correlation between the UF-1000i and quantitative manual microscopy. METHODS: A total of 214 untreated urine samples were studied using the Sysmex UF-1000i and compared with results obtained from quantitative manual microscopy using the Fuchs-Rosenthal counting chamber. RESULTS: Using Pearson statistics, we observed satisfactory correlation between the UF-1000i and quantitative microscopy: for red blood cells (RBCs) r was 0.98, for white blood cells (WBCs) r was 1.00, for epithelial cells (EC) r was 0.96, and for casts r was 0.69. Using linear regression statistics, we also observed satisfactory correlation between the UF-1000i and quantitative microscopy: for RBCs R(2) was 0.95, for WBCs R(2) was 0.99, for EC R(2) was 0.92, and for casts R(2) was 0.48. CONCLUSIONS: In our experience, automated urine particle analysis performed using the Sysmex UF-1000i analyzer is sufficiently precise and improves the workflow in a routine laboratory. Precision was satisfactory and concordance with the reference method is good for RBC, WBC and EC; for casts microscopic observation is required for flagged samples to discriminate hyaline from pathologic casts.

Cutoff values for bacteria and leukocytes for urine flow cytometer Sysmex UF-1000i in urinary tract infections.

Because urinary tract infections (UTIs) are a quite common disease, the gold standard for diagnosing UTIs is still bacterial culture, although a large percentage of samples are negative: unnecessary cultures can be reduced by means of an effective screening test. The analytic performance of a new urine cytometer, the UF-1000i, has been tested on 1463 urine samples submitted to our laboratory for culture. Bacteria and leukocyte counts have been compared by means of the UF-1000i with colony-forming unit (CFU) quantification on citrate lactose electrolytes deficient agar to assess the best cutoff values. By using quantitative cultures and considering as positive a sample with 10 x 10(5) CFU/mL, 546 positive samples (37%) were observed. If compared with 10 x 10(5) CFU/mL, the cutoff values obtained were 125 bacteria/microL and 40 leukocytes/ microL, respectively. Analytic parameters such as sensitivity, specificity, positive predictive value, negative predictive value, and correctly classified incidence were satisfactory. Based on the results obtained in this study, when using the UF-1000i analyzer for a screening test for UTI, a cutoff value of 40 white blood cells/microL should be adopted. The cutoff value for bacteria should be 125/microL for those clinical conditions in which 10 x 10(5) CFU/mL indicates a positivity.