Urinalysis highly accurate for diagnosing UTI in young febrile infants
Urinalysis provides a highly sensitive and specific means of screening for urinary tract infections (UTIs) in young febrile infants with or without concurrent bacteraemia, according to a study.
“The group of infants with UTIs and bacteraemia appears to represent a patient population with an extremely high likelihood of having ‘true’ UTIs, whereas a population of febrile infants with bacterial growth in the urine but without bacteraemia may at times include patients with asymptomatic bacteriuria,” the investigators said.
“Our results do confirm, however, that the urinalysis is a highly accurate screening test even in the youngest infants with UTIs, regardless of bacteraemia status,” they added.
The current study was a secondary analysis of data from a prospective study of 4,147 febrile infants aged ≤60 days who underwent urinalysis. A positive urinalysis was defined by the presence of any leukocyte esterase (LE), nitrite or pyuria (>5 white blood cells per high-power field).
A total of 289 infants (7.0 percent) had UTIs defined by the growth of ≥50,000 colony-forming units (CFUs)/mL of a urinary pathogen. Of these infants, 27 (9.3 percent) presented with bacteraemia. [Pediatrics 2018;doi:10.1542/peds.2017-3068]
Urinalysis findings were positive for LE or pyuria and were negative for nitrites in most infants with UTIs. The presence of moderate or large LEs were noted in all patients with bacteraemia.
The aggregate urinalysis was able to diagnose UTIs with ≥50,000 CFUs/mL with sensitivities of 0.94 (95 percent CI, 0.91–0.97) regardless of bacteraemia status, 1.00 (0.87–1.00) with bacteraemia and 0.94 (0.90–0.96) without bacteraemia. Specificity was 0.91 (0.90–0.91) across all groups.
For UTIs with colony counts ≥10,000 CFUs/mL, urinalysis demonstrated less sensitivity (0.87; 0.83–0.90) but similar specificity (0.91; 0.90–0.92). The sensitivity of the urinalysis for such UTIs with bacteraemia remained very high (1.00; 0.88–1.00), whereas that for UTIs without bacteraemia was lower (0.86; 0.82–0.89).
Based on the present data, the investigators pointed out that the urinalysis may provide valuable and reliable information to clinicians evaluating the youngest febrile infants for serious bacterial infections.
“Indeed, the urinalysis had perfect sensitivity and negative predictive values for UTIs associated with bacteraemia and revealed excellent performance for UTIs without bacteraemia,” they said. “The performance of the [test] remained high, although with slightly lower sensitivity, when UTI was defined by a lower colony count [ie, ≥10,000 CFUs/mL].”
The study was not without limitations. As the investigators acknowledged, there was no information regarding the specific laboratory methods used to complete the urinalyses. Additionally, the study used a UTI definition based solely on urine culture.