Diagnosis of bacteriuria and leukocyturia by automated flow cytometry compared with urine culture

J Clin Microbiol. 2010 Nov;48(11):3990-6. doi: 10.1128/JCM.00975-10. Epub 2010 Aug 25.

Abstract

Urinary tract infection (UTI) is a widespread disease, and thus, the most common samples tested in diagnostic microbiology laboratories are urine samples. The "gold standard" for diagnosis is still bacterial culture, but a large proportion of samples are negative. Unnecessary culture can be reduced by an effective screening test. We evaluated the performance of a new urine cytometer, the Sysmex UF-1000i (Dasit), on 703 urine samples submitted to our laboratory for culture. We compared bacteria and leukocyte (WBC) counts performed with the Sysmex UF-1000i to CFU-per-milliliter quantification on CPS agar to assess the best cutoff values. Different cutoff values of bacteria/ml and WBC/ml were compared to give the best discrimination. On the basis of the results obtained in this study, we suggest that when the Sysmex UF-1000i analyzer is used as a screening test for UTI the cutoff values should be 65 bacteria/ml and 100 WBC/ml. Diagnostic performance in terms of sensitivity (98.2%), specificity (62.1%), negative predictive value (98.7%), positive predictive value (53.7%), and diagnostic accuracy (73.3%) were satisfactory. Screening with the Sysmex UF-1000i is acceptable for routine use. In our laboratory, we have reduced the number of bacterial cultures by 43%, speeded up their reporting, and decreased the inappropriate use of antibiotics.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Bacteria / isolation & purification*
  • Bacterial Load
  • Bacteriological Techniques / methods*
  • Bacteriuria / diagnosis
  • Child
  • Child, Preschool
  • Female
  • Flow Cytometry / methods*
  • Humans
  • Infant
  • Infant, Newborn
  • Leukocyte Count
  • Leukocytes*
  • Male
  • Middle Aged
  • Urinary Tract Infections / diagnosis*
  • Urine / cytology*
  • Urine / microbiology*
  • Young Adult