Urinary Neutrophil Gelatinase–Associated Lipocalin for the Diagnosis of Urinary Tract Infections

OBJECTIVES: To determine the accuracy of the novel biomarker urinary neutrophil gelatinase–associated lipocalin (uNGAL) to diagnose urinary tract infections (UTIs) in febrile infants and young children. METHODS: Prospective cross-sectional study of febrile infants RESULTS: Of 260 patients, 35 (13.5%) had UTIs. Median uNGAL levels were 215.1 ng/mL (interquartile range: 100.3–917.8) and 4.4 ng/mL (interquartile range: 1.6–11.8) in the groups diagnosed with and without UTIs, respectively. The area under the receiver-operating characteristic curve for uNGAL was 0.978 (95% confidence interval [CI]: 0.948–1.000). At a threshold uNGAL level of 39.1 ng/mL, sensitivity was 97.1% (95% CI: 83.4–99.9) and specificity was 95.6% (95% CI: 91.7–97.7). uNGAL had higher sensitivity than the combination of leukocyte esterase (in trace or greater amounts) or nitrite (+) (97.1%, 95% CI: 83.4–99.9 vs 74.3%, 95% CI: 56.4–86.9), with similar specificity (95.6%, 95% CI: 91.7–97.7 vs 97.3%, 95% CI: 94.0–98.9). uNGAL had higher sensitivity than Gram-stain (97.1%, 95% CI: 83.4–99.9 vs 74.3%, 95%: CI: 56.4–86.9), with similar specificity (95.6%, 95% CI: 91.7–97.7 vs 100.0%, 95% CI: 97.9–100.0). CONCLUSIONS: uNGAL has substantial accuracy to identify those with and without UTIs in infants and young children. Further studies will need to confirm our findings and determine if uNGAL is a more cost-effective test than standard screening tests.