title: Urinary Squamous Epithelial Cells Do Not Accurately Predict Urine Culture Contamination, but May Predict Urinalysis Performance in Predicting Bacteriuria.
abstract: OBJECTIVE
  The presence of squamous epithelial cells (SECs) has been advocated to identify urinary contamination despite a paucity of evidence supporting this practice. We sought to determine the value of using quantitative SECs as a predictor of urinalysis contamination.
  
  
  METHODS
  Retrospective cross-sectional study of adults (≥18 years old) presenting to a tertiary academic medical center who had urinalysis with microscopy and urine culture performed. Patients with missing or implausible demographic data were excluded (2.5% of total sample). The primary analysis aimed to determine an SEC threshold that predicted urine culture contamination using receiver operating characteristics (ROC) curve analysis. The a priori secondary analysis explored how demographic variables (age, sex, body mass index) may modify the SEC test performance and whether SECs impacted traditional urinalysis indicators of bacteriuria.
  
  
  RESULTS
  A total of 19,328 records were included. ROC curve analysis demonstrated that SEC count was a poor predictor of urine culture contamination (area under the ROC curve = 0.680, 95% confidence interval [CI] = 0.671 to 0.689). In secondary analysis, the positive likelihood ratio (LR+) of predicting bacteriuria via urinalysis among noncontaminated specimens was 4.98 (95% CI = 4.59 to 5.40) in the absence of SECs, but the LR+ fell to 2.35 (95% CI = 2.17 to 2.54) for samples with more than 8 SECs/low-powered field (lpf). In an independent validation cohort, urinalysis samples with fewer than 8 SECs/lpf predicted bacteriuria better (sensitivity = 75%, specificity = 84%) than samples with more than 8 SECs/lpf (sensitivity = 86%, specificity = 70%; diagnostic odds ratio = 17.5 [14.9 to 20.7] vs. 8.7 [7.3 to 10.5]).
  
  
  CONCLUSIONS
  Squamous epithelial cells are a poor predictor of urine culture contamination, but may predict poor predictive performance of traditional urinalysis measures.
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.|Division of Critical Care, Department of Anesthesia, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Mohr
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Karisa K
authors.initials: KK
authors.lastname: Harland
authors.affiliation: Department of Epidemiology, University of Iowa College of Public Health, Iowa City, IA.
authors.forename: Victoria
authors.initials: V
authors.lastname: Crabb
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Mutnick
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: David
authors.initials: D
authors.lastname: Baumgartner
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Spinosi
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Michael
authors.initials: M
authors.lastname: Haarstad
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Azeemuddin
authors.initials: A
authors.lastname: Ahmed
authors.affiliation: Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.|Iowa City Veterans Administration Health Care System, Iowa City, IA.
authors.forename: Marin
authors.initials: M
authors.lastname: Schweizer
authors.affiliation: Department of Emergency Medicine, University of Iowa Carver College of Medicine, Iowa City, IA.|Department of Pharmaceutical Care, University of Iowa Hospitals and Clinics, Iowa City, IA.
authors.forename: Brett
authors.initials: B
authors.lastname: Faine
mesh_terms: D000046:Academic Medical Centers; D000328:Adult; D000367:Age Factors; D000368:Aged; D001431:Bacteriological Techniques; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004847:Epithelial Cells / Q000166:cytology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012737:Sex Factors; D016482:Urinalysis / Q000592:standards*; D014552:Urinary Tract Infections / Q000175:diagnosis*; D014556:Urine / Q000166:cytology* / Q000382:microbiology*