25 Role of the urinalysis in managing infants less than 60 days old with a positive urine culture
Authors: Charles Steffany , Aycan Marissa , D’Alessandro Michelle , Latchman Andrew , Wahi Gita 
Published: October 2021

Abstract

Primary Subject area
Hospital Paediatrics

Background
Urinary tract infections (UTIs) in infants less than 60 days of age, often lead to hospitalization and intravenous antibiotic treatment. There are currently no national recommendations for the diagnosis and management of UTIs in this population. Historically, the urine culture alone was thought to be sufficient for diagnosing UTI due to concerns regarding the sensitivity of urinalysis (UA) in young infants. However, there is evidence that in children of all ages, the absence of pyuria in children with UTIs is rare. The role of the UA in influencing the current management of infants aged less than 60 days, with a positive urine culture, remains unclear.

Objectives
The objective of this study was to describe the characteristics of infants aged less than 60 days old with a positive urine culture. Specifically, we sought to: 1) determine the differences in clinical and biochemical characteristics of infants with a positive UA versus a negative UA; and 2) determine if UA result was associated with length of intravenous antibiotic treatment.

Design/Methods
We completed a retrospective cohort study of infants aged 0 to 60 days with a positive urine culture, cared for in a Canadian tertiary care children’s hospital between April 2016 and March 2019. Patients with a history of prematurity and those with a concomitant bacteremia or meningitis were excluded. A positive urine culture was defined as greater than 10,000 CFU/ml of a single organism obtained from a catheter specimen. A positive UA was defined by positive nitrites and/or a positive leukocyte esterase screen, and/or pyuria (greater than 5 white blood cells per high power field). Clinical and biochemical characteristics of infant groups with a positive UA, versus negative UA, were compared. Linear regression analysis was used to understand the association between UA result and length of intravenous antibiotic treatment.

Results
A total of 718 charts were screened. Eighty-nine patients met inclusion criteria, of which 52 (58%) had a positive UA and 37 (42%) had a negative UA. Of the 89 included infants, the average age was 32.5 days (SD 16.7), 31.5% were female, 79.8% had fever at presentation, and the average length of stay was 5.6 days (SD 2.9). Patients with a positive UA were more often febrile at presentation (90.3% vs. 64.9%, p = 0.006), and had a higher CRP (51.0, SD 56.1 vs. 8.1, SD 13.0), p &lt; 0.001), higher white blood cell count (15.2, SD 6.0 vs. 11.0, SD 5.7, p= 0.002), and more often had urine culture growth of E. Coli (96.2% vs. 62.9%, p &lt; 0.001). UA result was not associated with length of intravenous antibiotic treatment (p= 0.15).

Conclusion
This study demonstrates that infants with a positive urine culture and a positive UA result had more characteristics of infection, including fever, elevated CRP, elevated white blood cell count, and growth of E. Coli uropathogen, compared to infants with a negative UA. Despite this difference, there was no significant difference in length of intravenous antibiotic treatment between UA-positive versus UA-negative groups. This study suggests that infants with clinical and biochemical findings supportive of a UTI more often had a positive UA, along with a positive culture, and that the UA should be used as a screening test for UTI in infants aged less than 60 days.