TFRC and anemia (phenotype): However, due to its correlation with erythropoiesis, its levels also increase in response to enhanced erythropoietic activity, which poses a limitation.32 While the sTfR/log ferritin index has been proposed to improve diagnostic accuracy in anaemia classification compared to sTfR alone, the routine use of both soluble sTfR and the sTfR/log ferritin index remains limited due to cost considerations and significant analytical challenges.