Objective To investigate the changes and diagnostic significance in plasma undercarboxylated osteocalcin in children with Kawasaki disease (KD),especially with coronary artery lesions (CALs).Methods The data of 36 KD children were collected,who were inpatients at Department of Cardiovascular and Rheumatology,Shanxi Province Children's Hospital from January 2015 to December 2015,including 20 boys and 16 girls,aged (2.3 ± 1.1)years old.According to the course of the disease,KD children were divided into an acute stage group and a subacute stage group.Based on the echocardiography findings,KD children were subdivided into CALs group and no coronary artery lesions (NCALs) group.Twenty-five healthy children from the physical examination during the same period were selected as the healthy control group,13 boys and 12 girls,aged (2.6-± 1.0) years old.Plasma undercarboxylated osteocalcin level was measured by double antibody sandwich enzyme-linked immunosorbent method.Sigrnaplot 12.5software was used to analyze the data statistically,and the receiver-operating characteristic (ROC) curve was used to evaluate the diagnostic effect of plasma undercarboxylated osteocalcin in KD with CALs.Results The levels of plasma undercarboxylated osteocalcin in the healthy control group,the acute stage group and the subacute stage group were (16.4 ± 1.6) μg/L,(14.2 ± 1.6) μg/L,(14.3-± 1.7) μg/L,respectively.Compared with the healthy control group,the plasma undercarboxylated osteocalcin level in the acute stage and the subacute stage were significantly lower,the differences were statistically significant (q =6.088,5.687,all P ＜ 0.01).But there was no difference of plasma undercarboxylated osteocalcin level between the acute stage group and the subacute stage group (q =0.466,P ＞ 0.05).The levels of plasma undercarboxylated osteocalcin in acute stage group with CALs and acute stage group with NCALs were (12.9 ± 1.2) μg/L,(15.0 ± 1.4) μg/L.Compared with healthy control group,the plasma undercarboxylated osteocalcin levels of children with CALs and with NCALs were obviously decreased,the differences were statistically significant (q =8.711,3.891,all P ＜ 0.01).There was a statistical difference in plasma undercarboxylated osteocalcin level between the acute stage with CALs and the acute stage with NCALs (q =5.171,P ＜ 0.01).The plasma undercarboxylated osteocalcin levels of KD children with CALs in the subacute stage was (13.0-± 1.3) μg/L.Compared with acute stage,there was no statistical difference (t =0.257,P ＞ 0.05).There was a sensitivity of 79％,specificity of 82％,positive predictive value of 88％ and negative predictive value of 70％ for the 15.7 μg/L undercarboxylated osteocalcin for diagnosing KD.There was a sensitivity of 83％,specificity of 88％,positive predictive value of 83％ and negative predictive value of 88％ for the 13.7 μg/L undercarboxylated osteocalcin for diagnosing KD with CALs.Conclusions Osteocalcin is related to the pathogenesis and development of KD.Plasma undercarboxylated osteocalcin contributes to the diagnosis of KD with CALs.