Novel urine biomarkers to distinguish UTI from culture-negative pyuria

Background Emergency departments (EDs) often rely on urinalysis (UA) to rapidly identify urinary tract infections (UTIs) in children. However, the suboptimal test characteristics of UA can lead to false-positive results. Novel urinary biomarkers may increase the diagnostic precision of UA. In this study, we compared the concentrations of 6 pre-selected proteins: BH3 interacting domain death agonist (BID), B-cell lymphoma 6 protein, ras GTPase-activating protein 1, cathepsin S (CTSS), 3-hydroxyanthranilate 3,4-dioxygenase, and transgelin-2. Methods In a pediatric ED, we prospectively enrolled 167 children with UA and urine culture collected. Pyuria was defined as either >= 5 white blood cells per high-power field on microscopy or positive leukocyte esterase (LE). The urine culture was considered positive if it yielded >= 50,000 colony-forming units per milliliter of any single urinary pathogen. Urine protein levels were measured by enzyme-linked immunosorbent assay and normalized to urine creatinine. Results BID was significantly higher in the UTI group compared to the culture-negative pyuria group with a mean ratio of 1.42 (95% confidence interval (CI), 1.15, 1.76) when uncorrected for creatinine concentration. When corrected for creatinine concentration, CTSS was significantly elevated in the UTI group compared to the culture-negative pyuria group with a mean ratio of 2.11 (95% CI, 1.39, 3.21). Conclusions BID and CTSS concentrations were elevated in the urine of children with UTI compared to those with culture-negative pyuria. These proteins deserve further research into their utility to serve as novel biomarkers for UTI.