UTILITY OF GRAM STAINING IN THE DIAGNOSIS OF URINARY TRACT INFECTIONS IN PEDIATRIC PATIENTS

Introduction. The diagnosis of urinary tract infection (UTI) in infants without bladder control remains controversial, despite the availability of multiple diagnostic methods, such as the dipstick (DS), urinary sediment, flow cytometry, and Gram staining. Although Gram staining is commonly used, few studies have evaluated its effectiveness in the clinical diagnosis of UTI. Objectives. To assess the validity of Gram staining, both independently and in combination with the results of the urine dipstick, for diagnosing UTI. Materials and methods. Urine samples from 510 pediatric patients with suspected UTI, treated at the Pediatric Emergency Service, were analyzed using urine culture and Gram staining. Additionally, 397 of these patients under went dipstick testing. Patient ages ranged from 3 months to 17 years, with 427 children under 3 months and 83 over 3 months. Results. Of the cultures, 154 were positive, 335 negative, and 21 contaminated. The sensitivity of Gram staining was 90.3% (95% CI: 84.2-94.3%) and its spec-ificity was 93.1% (95% CI: 89.7-95.5%). The combined negative likelihood ratio for Gram staining and dipstick testing was 0.003, with a post-test negative probability of 0.1% in the fever without focus scenario. Conclusions. Gram staining, especially when combined with the dipstick test, is the most effective diagnostic tool for UTI in emergency settings, due to its high concor-dance with urine culture and its positive likelihood ratio. A negative Gram stain alone does not rule out UTI, but the combination of a negative dipstick and negative Gram stain allows for the exclusion of UTI in the emergency department.