Urinary tract infections (UTIs) are among the most common bacterial infections in young children and can cause a lot of damage if not diagnosed and treated in a timely fashion.
It is thus important that our screening tests are as accurate as possible. In recent years, some of the commonly used screening tests (dipstick and microscopic urinalysis) have become increasingly performed on automated analyzers.
Dr. Nader Shaikh and colleagues at the Children’s Hospital of Pittsburgh, Cincinnati Children’s Hospital, and Children’s National Hospital looked at the sensitivity and specificity of commonly used screening tests for UTI in detecting pyuria, or the presence of white blood cells (WBCs) in the urine. Their article, entitled “Accuracy of Screening Tests for the Diagnosis of Urinary Tract Infection in Young Children,” is being early released in Pediatrics this month (10.1542/peds.2024-066600).
The authors analyzed urine samples that were collected by catheterization from 4188 children 1–35 months of age. Only samples that had results from both urinalysis and culture were included.
Using a positive urine culture (defined as growth of at least 50,000 CFU/mL of a single organism), they compared 5 methods for assessing pyuria as a screening test for UTI:
- Leukocyte esterase on dipstick
- Manual WBC count using a hemocytometer
- Manual WBC count without using a hemocytometer
- Automated WBC count using flow cytometry
- Automated WBC enumeration using digital imaging with particle recognition.
Approximately 10% of the urine cultures were positive. Overall, sensitivity of the screening tests ranged from 76% to 88%. Thus, 12% to 24% of UTIs were missed on the screening tests.
In an invited commentary (10.1542/peds.2024-068242), Drs. Brian Becknell and Joshua Watson from Nationwide Children’s Hospital agree that if we depend upon “urinalysis with reflex culture”—which is when the urine culture is only done when the urinalysis is abnormal—to diagnose UTIs in young children, we will miss children with UTI who do not have pyuria.
My takeaways from this article and commentary are that young children can have culture-proven UTI without pyuria, and if you are concerned enough about the possibility of UTI in a young child to send a urinalysis, then it is probably better to order a separate urine culture rather than a reflex culture that depends on the presence of pyuria to be performed.
