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

• Published in: Diagnostic microbiology and infectious disease Vol. 65; no. 2; pp. 103 - 107
• Main Authors: Manoni, Fabio, Fornasiero, Lucia, Ercolin, Mauro, Tinello, Agostino, Ferrian, Melissa, Hoffer, Paolo, Valverde, Sara, Gessoni, Gianluca
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.10.2009; Elsevier
• Subjects: Adult; Bacterial diseases; Bacterial diseases of the urinary system; Bacteriuria; Biological and medical sciences; Clinical Laboratory Techniques - methods; Colony Count, Microbial; Flow Cytometry - methods; Fundamental and applied biological sciences. Psychology; Human bacterial diseases; Humans; Infectious Disease; Infectious diseases; Internal Medicine; Leukocyte Count; Medical sciences; Microbiology; Predictive Value of Tests; Pyuria; Rapid diagnosis; Sensitivity and Specificity; UF-1000i; Urinary tract infection; Urinary Tract Infections - diagnosis; Urinary Tract Infections - microbiology; Urinary Tract Infections - pathology; Urine - cytology; Urine - microbiology; Rapid diagnosis; Urinary tract infection; Bacteriuria; UF-1000i; Pyuria; Urine; Flow cytometry; Urinary system disease; Microbiology; Leukocyte; Urinary tract disease; Bacteria; Diagnosis
• ISSN: 0732-8893; 1879-0070
• DOI: 10.1016/j.diagmicrobio.2009.06.003

Abstract 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 × 105 CFU/mL, 546 positive samples (37%) were observed. If compared with 10 × 105 CFU/mL, the cutoff values obtained were 125 bacteria/μL and 40 leukocytes/ μL, 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/μL should be adopted. The cutoff value for bacteria should be 125/μL for those clinical conditions in which 10 × 105 CFU/mL indicates a positivity.