BackgroundTenascin-C (TN-C) is an extracellular matrix glycoprotein related to tissue inflammation. Our previous retrospective study conducted in 2016 revealed that the serum tenascin-C level was higher in patients with Kawasaki disease (KD) who were resistant to intravenous immunoglobulin (IVIG) and developed coronary artery lesions (CALs). The present study is a prospective cohort study to assess if the serum level of tenascin-C could be used as a novel biomarker to predict the risk of resistance to initial treatment for high-risk patients.MethodsA total of 380 KD patients were registered and provided serum samples for tenascin-C measurement before commencing their initial treatment. Patients who did not meet the inclusion criteria were excluded from analysis; of the 181 remaining subjects, there were 144 low-risk patients (Kobayashi score: ≤4 points) and 37 high-risk patients (Kobayashi score: ≥5 points). The initial treatments for low-risk patients and high-risk patients were conventional therapy (IVIG with aspirin) and prednisolone combination therapy, respectively. The patient clinical and laboratory data, including the serum tenascin-C level, were compared between initial treatment responders and non-responders.ResultsIn the low-risk patients, there was no significant difference in the median levels of serum tenascin-C between the initial therapy responders and non-responders. However, in the high-risk patients, the median serum tenascin-C level in initial therapy non-responders was significantly higher than that in initial therapy responders (175.8 ng/ml vs 117.6 ng/ml).ConclusionsSerum tenascin-C could be a biomarker for predicting the risk of high-risk patients being non-responsive to steroid combination therapy.Trial registrationThis study was a prospective cohort study. It was approved by the ethics committee of each institute and performed in accordance with the Declaration of Helsinki.