Performances of serum creatinine, C-reactive protein and white blood cell to predict urinary tract infection in febrile children younger than 24 months of age

Purpose: Differentiation of urinary tract infection (UTI) from viral infection is a critical challenge in febrile children in emergency departments (EDs). This study aimed to assess the predicting performances of creatinine, C-reactive protein (CRP), and white blood cell (WBC) for predicting UTI in the children. Methods: This study was a retrospective analysis of a prospectively enrolled cohort of febrile children who presented to our children’s hospital ED from August 2016 through February 2018. We included previously healthy, febrile (≥ 38。C) children younger than 24 months whose urine cultures were obtained. Accuracy of creatinine, CRP, and WBC were assessed by optimal cutoffs, which were calculated using receiver operating characteristic curves. Results: Among the total 33,013 children to the ED, 7,847 (23.8%) febrile children were registered to the fever registry. Finally, 506 children were included, and UTI was diagnosed in 127 (25.1%). The areas under the curve of creatinine, CRP, and WBC to predict UTI were 0.41 (95% confidence interval [CI], 0.35-0.46), 0.71 (95% CI, 0.66-0.77), and 0.66 (95% CI, 0.60-0.72), respectively. The cutoffs were 0.26 mg/dL for creatinine, 2.3 mg/dL for CRP, and 14.4 × 10 cells/μL for WBC. Creatinine showed worse performance than the other variables. The application of creatinine added to the other variables led to an increase only in the sensitivity, but at the expense of a lower specificity, positive predictive value, and negative predictive value. Conclusion: Serum creatinine showed a poor performance in predicting UTI in the febrile young children. Since a single biomarker can neither rule in nor rule out UTI in the children, the prediction of UTI can be achieved by the interpretation of both clinical and laboratory findings.