AFP and chronic kidney disease: In addition, Xiaofang et al. demonstrated that, in CKD patients without benign or malignant tumors, the serum concentrations of CA19-9, CA125 (in males), cytokeratin fragment 21-1, NSE, and squamous cell carcinoma antigen were positively correlated with renal function decline, while there were no significant differences in the concentrations of CA125 (in females), AFP, CA15.3 or CA72.4 [19].