Quantitative evaluation of pyuria with a hemocytometer in children on clean intermittent catheterization

Urinalysis is commonly used to diagnose urinary tract infections (UTIs), but its accuracy is reduced in children undergoing clean intermittent catheterization (CIC) because of asymptomatic pyuria. This study aimed to determine the optimal urinary leukocyte cutoff value for diagnosing UTIs using a hemocytometer.

This retrospective observational study included children (<16 years) on CIC at a tertiary children's hospital between April 2020 and March 2025. Quantitative urinalysis was performed using a UF-1500 hemocytometer. UTI was defined as bacteriuria ≥10⁴ CFU/mL accompanied by antimicrobial treatment. Receiver operating characteristic (ROC) curve analysis was used to identify the optimal cutoff for urinary white blood cell (WBC) count.

Among 134 patients (2871 specimens), 101 specimens were classified as infection cases (3.5%). Median urinary WBC counts were markedly higher during infection (1514.6/mm³) than during non-infectious periods (21.2/mm³; p < 0.001). ROC analysis yielded an area under the curve of 0.950 (95% CI, 0.935-0.964). The optimal cutoff value was 220.8/mm³, corresponding to 94.1% sensitivity, 84.7% specificity, and 99.7% negative predictive value. WBC counts did not significantly differ among infections caused by different uropathogens.

Hemocytometer-based quantification of pyuria provided high diagnostic accuracy and may be particularly useful as a rule-out test for UTIs in children undergoing CIC.