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.
Manoni
Fabio
F
Service of Laboratory Medicine, Civil Hospital, 35043 Monselice, Padua, Italy.
Fornasiero
Lucia
L
Ercolin
Mauro
M
Tinello
Agostino
A
Ferrian
Melissa
M
Hoffer
Paolo
P
Valverde
Sara
S
Gessoni
Gianluca
G
D000328:Adult; D019411:Clinical Laboratory Techniques / Q000379:methods*; D015169:Colony Count, Microbial; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D007958:Leukocyte Count; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014552:Urinary Tract Infections / Q000175:diagnosis* / Q000382:microbiology / Q000473:pathology; D014556:Urine / Q000166:cytology* / Q000382:microbiology*