Indeterminate QuantiFERON Results in Pediatric Kawasaki Disease: Inflammatory Predictors and Diagnostic Implications.

Introduction Interferon-gamma release assays (IGRAs), such as the QuantiFERON®-TB Gold Plus (QFT), are widely used for tuberculosis (TB) screening in children. However, indeterminate QFT results remain a diagnostic challenge, particularly in patients with Kawasaki disease (KD), in whom systemic inflammation may transiently impair T-cell function. This study aimed to identify clinical and laboratory factors associated with indeterminate QFT results in pediatric patients, with a focus on KD. Methods We retrospectively analyzed 147 pediatric QFT tests performed at a tertiary medical center in Japan between September 2019 and May 2025. Clinical characteristics and laboratory parameters were compared between patients with indeterminate and negative QFT results. Subgroup analyses were conducted for children with KD. Results Among the 147 pediatric cases, 30 (20.4%) yielded indeterminate QFT results, 24 (80%) of which involved KD. In the KD subgroup, the indeterminate group had significantly higher C-reactive protein levels (median 5.65 vs. 3.21 mg/dL; p=0.016) and lower serum albumin levels (2.75 vs. 2.90 g/dL; p=0.013) compared to the negative group. No significant differences were observed in other laboratory parameters. Conclusion This study suggests that QFT may yield indeterminate results in pediatric KD during the acute inflammatory phase, potentially reflecting transient inflammation-induced T-cell suppression. Clinicians should consider the timing of IGRA testing, alternative assays such as T-SPOT.TB, and adjunctive diagnostic tools when screening for TB in this population.