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Urine Concentration and Pyuria for Identifying UTI in Infants.
Pediatrics. 2016 11; 138(5)Ped

Abstract

BACKGROUND

Varying urine white blood cell (WBC) thresholds have been recommended for the presumptive diagnosis of urinary tract infection (UTI) among young infants. These thresholds have not been studied with newer automated urinalysis systems that analyze uncentrifuged urine that might be influenced by urine concentration. Our objective was to determine the optimal urine WBC threshold for UTI in young infants by using an automated urinalysis system, stratified by urine concentration.

METHODS

Retrospective cross-sectional study of infants aged <3 months evaluated for UTI in the emergency department with paired urinalysis and urine culture. UTI was defined as ≥50 000 colony-forming units/mL from catheterized specimens. Test characteristics were calculated across a range of WBC and leukocyte esterase (LE) cut-points, dichotomized into specific gravity groups (dilute <1.015; concentrated ≥1.015).

RESULTS

Twenty-seven thousand infants with a median age of 1.7 months were studied. UTI prevalence was 7.8%. Optimal WBC cut-points were 3 WBC/high-power field (HPF) in dilute urine (likelihood ratio positive [LR+] 9.9, likelihood ratio negative [LR‒] 0.15) and 6 WBC/HPF (LR+ 10.1, LR‒ 0.17) in concentrated urine. For dipstick analysis, positive LE has excellent test characteristics regardless of urine concentration (LR+ 22.1, LR‒ 0.12 in dilute urine; LR+ 31.6, LR‒ 0.22 in concentrated urine).

CONCLUSIONS

Urine concentration should be incorporated into the interpretation of automated microscopic urinalysis in young infants. Pyuria thresholds of 3 WBC/HPF in dilute urine and 6 WBC/HPF in concentrated urine are recommended for the presumptive diagnosis of UTI. Without correction of specific gravity, positive LE by automated dipstick is a reliably strong indicator of UTI.

Authors+Show Affiliations

Division of Emergency Medicine, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts pradip.chaudhari@childrens.harvard.edu.Division of Emergency Medicine, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts.Division of Emergency Medicine, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

27940788

Citation

Chaudhari, Pradip P., et al. "Urine Concentration and Pyuria for Identifying UTI in Infants." Pediatrics, vol. 138, no. 5, 2016.
Chaudhari PP, Monuteaux MC, Bachur RG. Urine Concentration and Pyuria for Identifying UTI in Infants. Pediatrics. 2016;138(5).
Chaudhari, P. P., Monuteaux, M. C., & Bachur, R. G. (2016). Urine Concentration and Pyuria for Identifying UTI in Infants. Pediatrics, 138(5).
Chaudhari PP, Monuteaux MC, Bachur RG. Urine Concentration and Pyuria for Identifying UTI in Infants. Pediatrics. 2016;138(5) PubMed PMID: 27940788.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Urine Concentration and Pyuria for Identifying UTI in Infants. AU - Chaudhari,Pradip P, AU - Monuteaux,Michael C, AU - Bachur,Richard G, Y1 - 2016/10/18/ PY - 2016/08/09/accepted PY - 2016/12/13/entrez PY - 2016/12/13/pubmed PY - 2017/6/27/medline JF - Pediatrics JO - Pediatrics VL - 138 IS - 5 N2 - BACKGROUND: Varying urine white blood cell (WBC) thresholds have been recommended for the presumptive diagnosis of urinary tract infection (UTI) among young infants. These thresholds have not been studied with newer automated urinalysis systems that analyze uncentrifuged urine that might be influenced by urine concentration. Our objective was to determine the optimal urine WBC threshold for UTI in young infants by using an automated urinalysis system, stratified by urine concentration. METHODS: Retrospective cross-sectional study of infants aged <3 months evaluated for UTI in the emergency department with paired urinalysis and urine culture. UTI was defined as ≥50 000 colony-forming units/mL from catheterized specimens. Test characteristics were calculated across a range of WBC and leukocyte esterase (LE) cut-points, dichotomized into specific gravity groups (dilute <1.015; concentrated ≥1.015). RESULTS: Twenty-seven thousand infants with a median age of 1.7 months were studied. UTI prevalence was 7.8%. Optimal WBC cut-points were 3 WBC/high-power field (HPF) in dilute urine (likelihood ratio positive [LR+] 9.9, likelihood ratio negative [LR‒] 0.15) and 6 WBC/HPF (LR+ 10.1, LR‒ 0.17) in concentrated urine. For dipstick analysis, positive LE has excellent test characteristics regardless of urine concentration (LR+ 22.1, LR‒ 0.12 in dilute urine; LR+ 31.6, LR‒ 0.22 in concentrated urine). CONCLUSIONS: Urine concentration should be incorporated into the interpretation of automated microscopic urinalysis in young infants. Pyuria thresholds of 3 WBC/HPF in dilute urine and 6 WBC/HPF in concentrated urine are recommended for the presumptive diagnosis of UTI. Without correction of specific gravity, positive LE by automated dipstick is a reliably strong indicator of UTI. SN - 1098-4275 UR - https://www.unboundmedicine.com/medline/citation/27940788/Urine_Concentration_and_Pyuria_for_Identifying_UTI_in_Infants_ DB - PRIME DP - Unbound Medicine ER -