BACKGROUND: Urinary tract infections (UTIs) are encountered frequently in children, and their early diagnosis and treatment are important. This study evaluates the diagnostic value of serum concentrations of lipopolysaccharide-binding protein (LBP), an acute-phase protein, in children with febrile UTI and compares it to those of the total white blood cell count (WBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), procalcitonin (PCT), and interleukin-6 (IL-6).METHODS: The study population comprised 77 consecutive patients with a first-episode febrile UTI (33 boys) with a median age of 11 months [interquartile range (IQR), 5.5-33 months], 21 healthy controls (11 boys) with a median age of 10 months (IQR, 5-20.5 months) and 58 febrile controls with a fever due to other causes (28 boys) with a median age of 12.5 months (IQR, 7-30 months). LBP, IL-6, PCT, and CRP were measured for both patients and control groups.RESULTS: The serum levels of LBP (p  <  0.001), CRP (p  <  0.001), PCT (p  =  0.001), IL-6 (p  =  0.002), ESR (p  =  0.020), and WBC (p  <  0.001) were higher in patients with febrile UTI than in the healthy and febrile control groups. The LPB cut-off value for best sensitivity and specificity in patients with febrile UTI was >43.23 mg/l. Furthermore, the area under the receiver operating characteristic curve was significantly greater for LBP than for CRP (p  =  0.014), PCT (p  <  0.001), ESR (p  <  0.001), WBC (p  =  0.002) and IL-6 (p  =  0.006).CONCLUSIONS: The results of this study suggest that the serum LBP concentration constitutes a reliable biologic marker for the diagnosis of a febrile UTI in children.