Background. Procalcitonin (PCT) is a new parameter of inflammation, the clinical usefulness of which is currently being evaluated.

Materials and methods. We determined simultaneously the serum concentrations of PCT and C-reactive protein (CRP) as well as the white blood cell (WBC) count in 25 patients with Kawasaki disease (KD), 17 with bacterial infections, 10 with systemic autoimmune diseases, 17 with viral infections and 18 healthy children. The optimal cut-off value of each parameter for predicting coronary aneurysms was determined using receiver operating characteristic curves.

Results. Significantly higher serum concentrations of PCT were observed in patients with KD (2.3±3.0 ng/ml) and bacterial infections (2.2±2.9 ng/ml) than in patients with autoimmune diseases (0.4±0.4 ng/ml) or viral infections (0.4±0.3 ng/ml), or in healthy children (0.2±0.1 ng/ml). The serum PCT but not the WBC count or CRP, differentiated the KD patients from the patients with autoimmune diseases. The optimal cut-off value of 3.0 ng/ml of PCT increased the prediction rate of coronary aneurysms that subsequently occurred in 4 (16%) patients with KD.

Conclusions. The serum PCT may be clinically useful for determining the severity of KD and for narrowing the differential diagnosis of patients with inflammatory diseases.