MDK and non-small cell lung carcinoma: As shown in the receiver operating characteristic (ROC) curve analysis, at a cut-off value of 400 pg/ml, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the serum midkine levels for identifying patients with NSCLC were 71.2%, 88.1%, 90.3%, 82.5% and 86.7%, respectively.