Nevertheless, the predictive effect of GDF 15 on survival of MM patients is still in debate, because current research results were different.[16,17] As for sTfR, it is thought that sTfR measurement may be the most important biomarker to uncover the etiology of anemia in MM compared to more established biomarkers, such as serum ferritin and C-reactive protein in theory. This evidence concerns the gene TFRC and anemia.