Erythema and induration of the Bacillus Calmette-Guérin site for diagnosing Kawasaki disease.

INTRODUCTION: Kawasaki disease (KD) is a challenging diagnosis. Erythema and induration of the Bacillus Calmette-Guérin (BCG) site is increasingly recognised as a significant clinical clue. However, there is little data to support its specificity or KD as compared to other febrile illnesses. We aimed to evaluate BCG reaction or induration as a diagnostic tool for KD.

METHODS: A retrospective case-controlled study of patients discharged with a diagnosis of KD from 2007 to 2010 was conducted. Another group of patients admitted over the same period for possible KD, but later found not to have KD, served as control.

RESULTS: Significantly more infants with KD (69.7%) had BCG site changes than older children (27.8%; p < 0.001). It also presented earlier in the course of KD; < 5 days (53.3%) compared to ≥ 5 days of fever (30.0%; p < 0.001). Positive predictive value of BCG site reaction or induration for KD was 90.8% (95% confidence interval [CI] 0.819-0.962) for infants and 96.2% (95% CI 0.868-0.995) for older children. The prevalence rate of changes at the BCG site was 9.9% among patients with non-KD febrile illnesses and 42.6% among patients with KD.

CONCLUSION: BCG site reaction or induration is a useful clinical clue for KD in both infants and older children, with a higher prevalence in infants. Physicians should consider KD in children with febrile illness and redness or crust formation at the BCG site, especially in view of low rates of BCG reaction or induration in non-KD febrile illnesses.