Bone marrow macrophage iron content and sideroblast count in iron- and ESA-naïve patients with CKD-related anemia

Since in chronic kidney disease (CKD) iron deficiency anemia (IDA) can coexist with inflammation-induced immobilization of iron in macrophages (anemia of chronic disorders - ACD), we assessed the utility of ferritin, transferrin saturation (TSAT), and hepcidin for differentiation of mixed IDA-ACD from ACD, using bone marrow (BM) examination as reference.

This cross-sectional, single-center study analyzed 162 non-dialysis iron and epoietin-naïve CKD patients (52% males, median age 67 years, eGFR 14.2 mL/min 1.73 m², hemoglobin 9.4 g/dL). BM aspiration, serum hepcidin (ELISA), ferritin, TSAT, and C-Reactive protein (CRP) were the main studied parameters.

ACD was seen in 51%, IDA-ACD in 40%, while "pure" IDA in only 9%. In univariate and binomial analyses, IDA-ACD differed from ACD by lower ferritin and TSAT, but not by hepcidin or CRP. Correspondingly, in receiver operating curve analysis, ferritin and TSAT differentiated IDA-ACD from ACD, at cutoffs of 165 ng/mL and 14%, but with moderate precision (sensitivity and specificity of 72%, and 61%, respectively).

The mixed pattern IDA-ACD could be more prevalent than estimated in non-dialysis CKD. Ferritin and, to a lesser degree, TSAT are useful in the diagnosis of IDA superimposed on ACD, while hepcidin, although reflecting BM macrophages iron, seems to have limited utility.