Serum soluble urokinase plasminogen activator receptor as a biomarker for distinguishing Kawasaki disease from infections in febrile children

ABSTRACT Background The soluble form of the urokinase plasminogen activator receptor (SuPAR) is a potential biomarker in various inflammatory, infectious, and autoimmune conditions. Objectives In this stusy, we aimed to evaluate its diagnostic utility in febrile children to distinguish between Kawasaki disease (KD) and infections, and to investigate any association with the development of coronary artery aneurysms (CAA) KD. Methods In this retrospective observational cohort study we enrolled 17 children with fever lasting more than 5 days and without suggestive diagnostic signs on admission to hospital. Serum SuPAR concentrations were measured on admission and compared between children with confirmed KD and those with infections, as well as between children with KD who did or did not develop CAA. Results KD was later confirmed in seven children (median age 25 months), and febrile infections in 10. There was no significant difference in suPAR concentrations between both groups: 5.35 ± 2.76 ng/mL in KD, and 5.57 ± 1.69 ng/mL in febrile infections ( p =0.84). The best cut-off value for suPAR, ≥ 7.74 ng/mL, was the best to correctly classify 64.7% of the cases, with a sensitivity of 28.6% and specificity of 90%. However, it had a low diagnostic performance (Youden index 18.6%, area under the curve curve 60%), and therefore failed to differentiate between KD and infections. In the seven children with KD, only one child developed CAA (SuPAR 4.69 ng/mL) while six other did not (SuPAR 5.47 ± 1.04 ng/mL) but the statistical significance could not be computed. Conclusion In febrile children, serum suPAR concentrations failed to distinguish between KD and infections, and were not associated with the development of CAA in KD. Therefore, SuPAR is not a useful biomarker in the diagnosis or prognosis of KD.