UA – Can You Trust It Under 60-Days?

February 23, 2018

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Sensitivity for UA with any leukocyte esterase (including trace), nitrite, or >5 WBCs/hpf was 94% for UTI growing >50,000 colony forming units (CFU).

Why does this matter?
Prior studies have found the sensitivity of the UA for true UTI to be in the mid 70s-80s.  This study suggests that in young infants, it is more accurate than that.

Can you believe the UA in infants <60-days?
This was a secondary analysis of prospectively collected data from the PECARN group.  Out of over 4000 infants under 60 days, 7% had UTI, defined as >50,000 CFU or a urinary pathogen.  A positive UA (defined as any leukocyte esterase, nitrite, or >5 WBCs/hpf) had a sensitivity of 94% overall; 100% in infants with bacteremia; specificity 91% for all.  The editorial notes, “The criterion of ≥50 000 CFU/mL remains the current standard, but clinicians may want to consider ≥10 000 CFU/mL in catheterized specimens from young infants who are at risk for UTI.”  Sensitivity for this threshold was 87%; specificity 91%.

Source
Accuracy of the Urinalysis for Urinary Tract Infections in Febrile Infants 60 Days and Younger. Pediatrics. 2018 Jan 16. pii: e20173068. doi: 10.1542/peds.2017-3068. [Epub ahead of print]
Editorial: The Diagnosis of UTI: Colony Count Criteria Revisited. Pediatrics. 2018 Jan 16. pii: e20173239. doi: 10.1542/peds.2017-3239. [Epub ahead of print]

Peer reviewed by Thomas Davis, MD.