Early features of Kawasaki disease with pyuria in febrile infants younger than 6 months

BACKGROUND: Children with Kawasaki disease (KD) and pyuria have been misdiagnosed with urinary tract infection (UTI). We compared clinical and laboratory features at admission between two groups of infants under 6 months of age who showed initial pyuria, to identify the initial clues suggestive of KD. METHODS: We retrospectively reviewed the medical records of children with fever who were under 6 months of age with pyuria, over a 10-year period (2007–2017). We included infants with sterile pyuria who were finally diagnosed with KD and those with UTI. RESULTS: During the period investigated, 12 (9.9%) KD patients with sterile pyuria and 378 infants with UTI were included in this study. Older age (P < 0.01), a longer duration of fever; total and before admission (P < 0.01), more negative nitrite test (P < 0.01), higher platelet count (P = 0.04), increased C-reactive protein (CRP) (P < 0.01) and erythrocyte sedimentation rate (ESR) (P < 0.01), were identified as initial features of infants finally diagnosed with KD. In the receiver operating characteristic analysis, optimal cut-off values of 509 k/μL for platelet count, 60 mg/L for CRP, and 68 mm/H for ESR were selected. Patients with ESR > 68 mm/hr had a ninefold higher odds of KD compared to those with lower ESR levels (odds ratio: 8.963, 95% confidence intervals: 1.936–41.493, P = 0.005), whereas CRP and platelet count could not significantly increase in the odds of KD at a cut-off point. CONCLUSION: Persistent fever, elevated ESR, and negative urine nitrite test can serve as early clues to suspect KD in febrile infants with pyuria.