Getting Specific About Urine Specific Gravity

Abstract

Research Article| February 01 2020 Getting Specific About Urine Specific Gravity AAP Grand Rounds (2020) 43 (2): 18. https://doi.org/10.1542/gr.43-2-18 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Getting Specific About Urine Specific Gravity. AAP Grand Rounds February 2020; 43 (2): 18. https://doi.org/10.1542/gr.43-2-18 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search toolbar search search input Search input auto suggest filter your search All PublicationsAll JournalsAAP Grand RoundsPediatricsHospital PediatricsPediatrics In ReviewNeoReviewsAAP NewsAll AAP Sites Search Advanced Search Topics: urinalysis, urine specific gravity, urinary tract infections, nitrites Source: Shaikh N, Shope MF, Kurs-Lasky M. Urine specific gravity and the accuracy of urinalysis. Pediatrics. 2019; 144(5): e20190467; doi: https://doi.org/0.1542/peds.2019-0467Google Scholar Investigators from the University of Pittsburgh conducted a retrospective analysis to determine whether urine specific gravity (SG) affects the accuracy of other components of the urinalysis. Children <24 months of age with a visit to the study ED between 2007 and 2013 were eligible if they underwent bladder catheterization and had an automated urinalysis and urine culture performed within 3 hours of each other. Children with genitourinary anomalies were excluded. Investigators evaluated the accuracy of urinalysis components used for diagnosis of UTI by comparing the positive likelihood ratios (LRs) in dilute versus concentrated urine samples. Dilute urine samples were defined as those with an SG <1.015, and concentrated samples were defined as those with an SG ≥1.015. UTI was defined as ≥100,000 colony-forming units (CFUs) per milliliter of a uropathogen from specimens obtained via clean catch or ≥50,000 CFU/mL from specimens obtained via catheterization. Urinalysis components evaluated included leukocyte esterase (LE; a positive test defined as ≥1), nitrite, white blood cell count (WBC) per high-power field (hpf; a positive test defined as ≥5), WBC/mm3 (a positive test defined as ≥10), bacteria/hpf (a positive test defined as ≥ few), and bacteria on Gram-stain (a positive test defined as ≥ any). Investigators also used predictive models to calculate how many children would be overtreated or missed with and without SG being used in the interpretation of other urinalysis components. There were 10,078 children included in analysis. Of these, 39.4% (n=3,966) had concentrated urine, and, overall, 6.1% had a UTI (n=617). The positive LRs for LE and bacteria/hpf (ie, their ability to rule in UTI) were similar in dilute and concentrated urine. However, WBC/hpf and WBC/mm3 had lower LRs in concentrated (vs dilute) urine, and nitrite and bacteria on Gram stain had higher LRs. Despite this finding, there was no change in predictive models for the number of children overtreated or missed with or without inclusion of SG in combination with urinalysis components. The investigators conclude that SG influences the accuracy of some components of the urinalysis but that inclusion of SG in decision-making would result in little change to clinical practice. Dr Bechtel has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device. UTIs are common bacterial infections in the pediatric population.1 An uncontaminated sample of urine for urinalysis and culture is generally required before starting any presumptive antimicrobial treatment. The urinalysis serves as the necessary screening test to determine the need to start empiric antibiotics, especially if pyuria and bacteriuria are present.2 Despite the widespread use of urinalyses by clinicians to make the presumptive diagnosis of UTI, urine SG has not previously been incorporated into their interpretation. For example, the urine SG has not been considered... You do not currently have access to this content.