Retrospective Evaluation of the Diagnostic Performance and Safety of a Reflex Urine Culture Algorithm in Pediatrics

Obtaining urine cultures (UCx) in the absence of symptoms and inflammation can result in misdiagnosis of urinary tract infections (UTIs) and inappropriate use of antibiotics. Reflex UCx is a diagnostic stewardship strategy in which a UCx is performed only if a urinalysis (UA) meets UTI criteria. We retrospectively applied a reflex UCx algorithm to assess its performance and safety in children.

From November 1, 2020, to July 23, 2023, we studied children aged >24 months to <18 years with paired UA and UCx, ie, a UTI evaluation, in emergency departments or inpatient units at our 8-hospital network. We assessed the diagnostic performance of pyuria of ≥10 white blood cells (WBC)/high power field (hpf) using a positive UCx as the reference standard; assessed reflex UCx exclusion criteria; and reviewed medical records of children with <10 WBC/hpf and positive UCx for signs and symptoms consistent with clinical UTI.

Of 79 960 UA and UCx, 10 226 UTI evaluations were eligible for inclusion. Of the 8.7% (890/10 226) positive UCx, 81.5% (725/890) had UA with ≥10 WBC/hpf, and 18.5% (165/890) had UA with <10 WBC/hpf. The sensitivity of ≥10 WBC/hpf was 81% and the negative predictive value (NPV) was 98%. Of 165 UTI evaluations with positive UCx and <10 WBC/hpf, 26% (43/165) met reflex UCx exclusion criteria, 58 (35%) met neither exclusion criteria nor clinical UTI definition, and 39% (64/165) not meeting exclusion criteria fulfilled the clinical UTI definition, representing 0.6% (64/10 226) of all UTI evaluations.

Retrospective application of a reflex UCx algorithm demonstrated high NPV and sensitivity, suggesting the algorithm had low risk for missing clinical UTIs and could have avoided unnecessary UCx.