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Quality indicators for urine sample contamination: can squamous epithelial cells and bacteria count be used to identify properly collected samples?

  • Gabriela Blauth Walber , José Antonio Tesser Poloni and Liane Nanci Rotta ORCID logo EMAIL logo
Published/Copyright: January 3, 2025
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Clinical Chemistry and Laboratory Medicine (CCLM)
From the journal Clinical Chemistry and Laboratory Medicine (CCLM) Volume 63 Issue 5

Abstract

Objectives

To evaluate urinalysis parameters useful for identifying mixed cultures in urine culture using an automated urinary particle analyzer to assess quality indicators (QIs) for urine sample contamination.

Methods

A retrospective observational cross-sectional study was conducted with 2,527 urine samples from patients of a quaternary hospital in Brazil. Urine samples were processed simultaneously in Sysmex UF-5000 flow cytometry analyzer (urinalysis) and MALDI-TOF (culture).

Results

For all samples, a cutoff of 123.8 bacteria/µL was established to discriminate culture-negative specimens. ROC curve indicated the following cutoffs for females and males, respectively: 193.65 and 23.55 bacteria/µL, and 21.35 and 5.05 squamous epithelial cells (SEC)/µL, with the latter two related to scenarios of sample contamination/colonization through mixed cultures. Performing univariate logistic regression, we found a 2.78 (CI95 %: 2.12–3.65) times higher chance of probable mixed culture when SEC values were above the cutoffs for each sex, and 6.91(CI95 %: 4.56–10.47) times for bacteria. For multivariate logistic regression, the OR values were 1.62 (CI95 %: 1.21–2.15) and 5.82 (CI95 %: 3.77–8.98), respectively.

Conclusions

The fluorescent flow cytometry analyzers could efficiently identify urinary bacteria counts associated with contamination/colonization scenarios using the cutoffs of 21.35 SEC/µL for women and 5.05 SEC/µL for men. The cutoffs for bacteria/µL (193.65 for females and 23.55 for males) indicated that the presence of bacteria in male samples may be more associated with urinary tract infections (UTIs), while in female samples, it may be associated with either UTIs or contamination/colonization scenarios. This makes the analyzer a helpful tool as QI of sample contamination in urine cultures.

Keywords: colonization; contamination; mixed cultures; quality indicators; squamous epithelial cells
Corresponding author: Liane Nanci Rotta, Graduate Program in Health Sciences, Federal University of Health Sciences of Porto Alegre, Sarmento Leite, 245 – Historic Center, CEP: 90.050-170 Porto Alegre, Brazil, E-mail:

Acknowledgments

We would like to thank the Carlos Franco Voegeli laboratory, from Santa Casa de Porto Alegre for the possibility of carrying out the study, and Cristiane Bündchen for the statistical assistance.

  1. Research ethics: The research related to human use has complied with all the relevant national regulations, institutional policies, and in accordance with the tenets of the Helsinki Declaration, and has been approved by the authors’ Institutional Review Board or equivalent committee (Santa Casa de Porto Alegre Research Ethics Committee, no. 4,577,958).

  2. Informed consent: Not applicable.

  3. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  4. Use of Large Language Models, AI and Machine Learning Tools: None declared.

  5. Conflict of interest: The authors state no conflict of interest.

  6. Research funding: None declared.

  7. Data availability: Not applicable.

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Received: 2024-06-10
Accepted: 2024-11-26
Published Online: 2025-01-03
Published in Print: 2025-04-28

© 2024 Walter de Gruyter GmbH, Berlin/Boston

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  1. Frontmatter
  2. Editorial
  3. Are the benefits of External Quality Assessment (EQA) recognized beyond the echo chamber?
  4. Reviews
  5. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part I – EQA in general and EQA programs in particular
  6. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part II – EQA cycles
  7. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part III – EQA samples
  8. Behind the scenes of EQA–characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part IV – Benefits for participant laboratories
  9. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part V – Benefits for stakeholders other than participants
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  18. Knowledge among clinical personnel on the impact of hemolysis using blood gas analyzers
  19. Quality indicators for urine sample contamination: can squamous epithelial cells and bacteria count be used to identify properly collected samples?
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  29. Letters to the Editor
  30. Concentrations and agreement over 10 years with different assay versions and analyzers for troponin T and N-terminal pro-B-type natriuretic peptide
  31. Does blood tube filling influence the Athlete Biological Passport variables?
  32. Influence of data visualisations on laboratorians’ acceptance of method comparison studies
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https://doi.org/10.1515/cclm-2024-1199
Keywords for this article
colonization; contamination; mixed cultures; quality indicators; squamous epithelial cells

Articles in the same Issue

  1. Frontmatter
  2. Editorial
  3. Are the benefits of External Quality Assessment (EQA) recognized beyond the echo chamber?
  4. Reviews
  5. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part I – EQA in general and EQA programs in particular
  6. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part II – EQA cycles
  7. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part III – EQA samples
  8. Behind the scenes of EQA–characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part IV – Benefits for participant laboratories
  9. Behind the scenes of EQA – characteristics, capabilities, benefits and assets of external quality assessment (EQA): Part V – Benefits for stakeholders other than participants
  10. Opinion Papers
  11. Not all biases are created equal: how to deal with bias on laboratory measurements
  12. Krebs von den Lungen-6 (KL-6) as a diagnostic and prognostic biomarker for non-neoplastic lung diseases
  13. General Clinical Chemistry and Laboratory Medicine
  14. Evaluation of performance in preanalytical phase EQA: can laboratories mitigate common pitfalls?
  15. Point-of-care testing improves care timeliness in the emergency department. A multicenter randomized clinical trial (study POCTUR)
  16. The different serum albumin assays influence calcium status in haemodialysis patients: a comparative study against free calcium as a reference method
  17. Measurement of 1,25-dihydroxyvitamin D in serum by LC-MS/MS compared to immunoassay reveals inconsistent agreement in paediatric samples
  18. Knowledge among clinical personnel on the impact of hemolysis using blood gas analyzers
  19. Quality indicators for urine sample contamination: can squamous epithelial cells and bacteria count be used to identify properly collected samples?
  20. Reference Values and Biological Variations
  21. Biological variation of cardiac biomarkers in athletes during an entire sport season
  22. Increased specificity of the “GFAP/UCH-L1” mTBI rule-out test by age dependent cut-offs
  23. Cancer Diagnostics
  24. An untargeted metabolomics approach to evaluate enzymatically deconjugated steroids and intact steroid conjugates in urine as diagnostic biomarkers for adrenal tumors
  25. Cardiovascular Diseases
  26. Comparative evaluation of peptide vs. protein-based calibration for quantification of cardiac troponin I using ID-LC-MS/MS
  27. Infectious Diseases
  28. The potential role of leukocytes cell population data (CPD) for diagnosing sepsis in adult patients admitted to the intensive care unit
  29. Letters to the Editor
  30. Concentrations and agreement over 10 years with different assay versions and analyzers for troponin T and N-terminal pro-B-type natriuretic peptide
  31. Does blood tube filling influence the Athlete Biological Passport variables?
  32. Influence of data visualisations on laboratorians’ acceptance of method comparison studies
  33. An appeal for biological variation estimates in deep immunophenotyping
  34. Serum free light chains reference intervals for the Lebanese population
  35. Applying the likelihood ratio concept in external quality assessment for ANCA
  36. A promising new direct immunoassay for urinary free cortisol determination
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