GDF15 and chronic kidney disease: Using the non-covariate analysis and Younden’s index, the optimum cut-off value of GDF-15 for diagnosing anemia among CKD participants was 723 ng/l (at a sensitivity of 82.98%and specificity of87.11%) Similarly, the optimum cut-off for hepcidin was 209 ng/dl (at a sensitivity of 80.85 and specificity of 85.11); A combination of the two parameters did not improve significantly the diagnostic value of either of the two tests (Table 5, Fig. 1).