Ann Lab Med.  2019 Sep;39(5):464-469. 10.3343/alm.2019.39.5.464.

Performance of the cobas u 701 Analyzer in Urinary Tract Infection Screening

• Ortiz de la Tabla V
• Gázquez G
• Infante A
• Martin C
• Buñuel F
• Gutiérrez F

• KMID: 2450969
• DOI: http://doi.org/10.3343/alm.2019.39.5.464

Abstract

BACKGROUND
Negative urine cultures to rule out urinary tract infections (UTI) generate a considerable laboratory workload; thus, a rapid screening test is desirable. We evaluated the performance of a new automated microscopy analyzer, cobas u 701 (Roche Diagnostics International, Rotkreuz, Switzerland) for the screening of UTI, and developed a rule-out strategy to reduce the number of samples requiring culture. We also assessed squamous epithelial cell (SEC) count as a predictor of culture contamination.
METHODS
In total, 1,604 urine samples from outpatients were analyzed with cobas u 701 and culture. Bacterial (BAC) and white blood cell (WBC) counts were used for sample interpretation. To determine a useful cut-off point to predict negative cultures, we selected the highest sensitivity and specificity values obtained from ROC curves. Diagnostic accuracy by age and gender was evaluated.
RESULTS
Urine culture showed growth of ≥104 colony forming units (CFU)/mL in 256 samples (16.0%). The highest sensitivity (91.8%) and specificity (68.4%) were obtained for cut-off points of 119 BAC/µL and 22 WBC/µL. The combination of BAC and WBC improved the performance of the rule-out strategy with a low rate of false-negative results (1.5%) and a high negative predictive value (NPV, 97.3%). Fifty-seven percent of the samples would not have required culture. SEC count was a poor predictor of culture contamination.
CONCLUSIONS
cobas u 701 can substantially reduce the number of urine samples requiring culture, with a low false-negative rate and a high NPV.

Keyword

Automated microscopy analyzer; cobas u 701; Screening urine samples; Urinary tract infection; Urine culture

MeSH Terms

Epithelial Cells
Humans
Leukocytes
Mass Screening
Microscopy
Outpatients
ROC Curve
Sensitivity and Specificity
Stem Cells
Urinary Tract Infections*
Urinary Tract*

Reference

1. Stalenhoef JE, van Dissel JT, van Nieuwkoop C. Febrile urinary tract infection in the emergency room. Curr Opin Infect Dis. 2015; 28:106–111. PMID: 25402776.

2. Okada H, Sakai Y, Miyazaki S, Arakawa S, Hamaguchi Y, Kamidono S. Detection of significant bacteriuria by automated urinalysis using flow cytometry. J Clin Microbiol. 2000; 38:2870–2872. PMID: 10921941.

3. Tessari A, Osti N, Scarin M. Screening of presumptive urinary tract infections by the automated urine sediment analyser sediMAX. Clin Chem Lab Med. 2015; 53(S2):s1503–s1508. PMID: 26509783.

4. Brilha S, Proença H, Cristino JM, Hänscheid T. Use of flow cytometry (Sysmex UF-100) to screen for positive urine cultures: in search for the ideal cut-off. Clin Chem Lab Med. 2010; 48:289–292. PMID: 19961394.

5. Evans R, Davidson MM, Sim LR, Hay AJ. Testing by Sysmex UF-100 flow cytometer and with bacterial culture in a diagnostic laboratory: a comparison. J Clin Pathol. 2006; 59:661–662. PMID: 16731608.

6. Zaman Z, Roggeman S, Verhaegen J. Unsatisfactory performance of flow cytometer UF-100 and urine strips in predicting outcome of urine cultures. J Clin Microbiol. 2001; 39:4169–4171. PMID: 11682551.

7. Jolkkonen S, Paattiniemi EL, Kärpänoja P, Sarkkinen H. Screening of urine samples by flow cytometry reduces the need for culture. J Clin Microbiol. 2010; 48:3117–3121. PMID: 20592157.

8. Oyaert M, Delanghe J. Progress in automated urinalysis. Ann Lab Med. 2019; 39:15–22. PMID: 30215225.

9. Falbo R, Sala MR, Signorelli S, Venturi N, Signorini S, Brambilla P. Bacteriuria screening by automated whole-field-image-based microscopy reduces the number of urine cultures. J Clin Microbiol. 2012; 50:1427–1429. PMID: 22238436.

10. Martinez MH, Bottini PV, Levy CE, Garlipp CR. UriSed as a screening tool for presumptive diagnosis of urinary tract infection. Clin Chim Acta. 2013; 425:77–79. PMID: 23906796.

11. Lee W, Ha JS, Ryoo NH. Comparison of the automated cobas u 701 urine microscopy and UF-1000i flow cytometry systems and manual microscopy in the examination of urine sediments. J Clin Lab Anal. 2016; 30:663–671. PMID: 26842372.

12. Kim SH, Song SA, Urm SH, Kook JK, Kim HR, Yong D, et al. Evaluation of the Cobas u 701 microscopy analyser compared with urine culture in screening for urinary tract infection. J Med Microbiol. 2017; 66:1110–1113.

13. Broeren MA, Bahçeci S, Vader HL, Arents NL. Screening for urinary tract infection with the SysmexUF-1000i urine flow cytometer. J Clin Microbiol. 2011; 49:1025–1029. PMID: 21248088.

14. Stürenburg E, Kramer J, Schön G, Cachovan G, Sobottka I. Detection of significant bacteriuria by use of the iQ200 automated urine microscope. J Clin Microbiol. 2014; 52:2855–2860. PMID: 24871218.

15. Kim H, Kim HR, Kim TH, Lee MK. Age-specific cutoffs of the Sysmex UF-1000i automated urine analyzer for rapid screening of urinary tract infections in outpatients. Ann Lab Med. 2019; 39:322–326. PMID: 30623625.

16. Íñigo M, Coello A, Fernández-Rivas G, Carrasco M, Marcó C, Fernández A, et al. Evaluation of the SediMax automated microscopy sediment analyzer and the Sysmex UF-1000i flow cytometer as screening tools to rule out negative urinary tract infections. Clin Chim Acta. 2016; 456:31–35. PMID: 26921459.

17. De Rosa R, Grosso S, Bruschetta G, Avolio M, Stano P, Modolo ML, et al. Evaluation of the Sysmex UF1000i flow cytometer for ruling out bacterial urinary tract infection. Clin Chim Acta. 2010; 411:1137–1142. PMID: 20359474.

18. Manoni F, Tinello A, Fornasiero L, Hoffer P, Temporin V, Valverde S, et al. Urine particle evaluation: a comparison between the UF-1000i and quantitative microscopy. Clin Chem Lab Med. 2010; 48:1107–1111. PMID: 20482296.

19. Mohr NM, Harland KK, Crabb V, Mutnick R, Baumgartner D, Spinosi S, et al. Urinary squamous epithelial cells do not accurately predict urine culture contamination, but may predict urinalysis performance in predicting bacteriuria. Acad Emerg Med. 2016; 23:323–330. PMID: 26782662.

20. Walter FG, Gibly RL, Knopp RK, Roe DJ. Squamous cells as predictors of bacterial contamination in urine samples. Ann Emerg Med. 1998; 31:455–458. PMID: 9546013.