Urine specific gravity, pyuria, and neutrophil gelatinase-associated lipocalin for identifying urinary tract infection in young children

Background To determine whether urine neutrophil gelatinase-associated lipocalin (uNGAL) might be superior to pyuria for detecting urinary tract infection (UTI) regardless of urine specific gravity (SG) in young children. Methods We conducted a retrospective analysis of children aged < 3 years who were evaluated for UTI with urinalysis, urine culture, and uNGAL measurements during a 5-year period. Sensitivity, specificity, likelihood ratios (LRs), predictive values (PVs), area under the curves (AUCs) of uNGAL cut-off levels, and various microscopic pyuria thresholds for detecting UTI were calculated for dilute (SG < 1.015) and concentrated urine (SG [greater than or equal to] 1.015). Results Of 456 children included, 218 had UTI. The diagnostic value of urine white blood cell (WBC) concentration to define UTI changed with urine SG. For detecting UTI, uNGAL cut-off of 68.4 ng/mL had higher AUC values than pyuria [greater than or equal to] 5 WBCs/high power field (HPF) for dilute and concentrated urine samples (both P 0.05). Positive LR and PV and specificity of uNGAL were all greater than those of pyuria [greater than or equal to] 5 WBCs/HPF regardless of urine SG, although the sensitivity of pyuria [greater than or equal to] 5 WBCs/HPF was higher than that of uNGAL cut-off for dilute urine (93.8% vs. 83.5%) (P < 0.05). At uNGAL [greater than or equal to] 68.4 ng/mL and [greater than or equal to] 5 WBCs/HPF, posttest probabilities of UTI were 68.8% and 57.5% for dilute urine and 73.4% and 57.3% for concentrated urine, respectively. Conclusions Urine SG can affect the diagnostic performance of pyuria for detecting UTI and uNGAL might be helpful for identifying UTI regardless of urine SG in young children. Graphical abstract
Author(s): Do Young Kim [sup.1] , Hyung Eun Yim [sup.1] , Min Hwa Son [sup.1] , Kee Hwan Yoo [sup.2] Author Affiliations: (1) grid.411134.2, 0000 0004 0474 0479, Department of [...]