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

Diagn Microbiol Infect Dis. 2009 Oct;65(2):103-7. 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 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.

Publication types

  • Evaluation Study

MeSH terms

  • Adult
  • Clinical Laboratory Techniques / methods*
  • Colony Count, Microbial
  • Flow Cytometry / methods*
  • Humans
  • Leukocyte Count
  • Predictive Value of Tests
  • Sensitivity and Specificity
  • Urinary Tract Infections / diagnosis*
  • Urinary Tract Infections / microbiology
  • Urinary Tract Infections / pathology
  • Urine / cytology*
  • Urine / microbiology*