Urinary squamous epithelial cells do not accurately predict urine culture contamination, but may predict urinalysis performance in predicting bacteriuria.
Acad Emerg Med. 2016 Jan 19;
Authors: Mohr NM, Harland KK, Crabb V, Mutnick R, Baumgartner D, Spinosi S, Haarstad M, Ahmed A, Schweizer M, Faine B
OBJECTIVES: 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, BMI) may modify the SEC test performance and whether SECs impacted traditional urinalysis indicators of bacteriuria.
RESULTS: Nineteen-thousand three-hundred twenty-eight records were included. Receiver operating curve analysis demonstrated that SEC count was a poor predictor of urine culture contamination (AUC 0.680, 95%CI 0.671 - 0.689). In secondary analysis, the positive likelihood ratio (LR+) of predicting bacteriuria via urinalysis among non-contaminated specimens was 4.98 (95% CI 4.59 - 5.40) in the absence of SECs, but the LR+ fell to 2.35 (95% CI 2.17 - 2.54) for samples with more than 8 SEC/lpf. In an independent validation cohort, urinalysis samples with fewer than 8 SEC/lpf predicted bacteriuria better (sensitivity 75%, specificity 84%) than samples with more than 8 SEC/lpf (sensitivity 86%, specificity 70%) [diagnostic odds ratio 17.5 (14.9 - 20.7) vs. 8.7 (7.3 - 10.5)].
CONCLUSION: Squamous epithelial cells are a poor predictor of urine culture contamination, but may predict poor predictive performance of traditional urinalysis measures. This article is protected by copyright. All rights reserved.
PMID: 26782662 [PubMed - as supplied by publisher]