Background: Iron deficiency (ID) is highly prevalent in chronic kidney disease (CKD) and it’s associated with poorer quality of life (QoL) and functional capacity. Intravenous iron therapy is limited to CKD patients with ID and anemia to avoid/delay the need or reduce the dose of erythropoiesis-stimulating agents, according to guidelines. We hypothesized that treatment with IV iron in CKD patients with ID and borderline anemia may improve their physical performance and QoL, independently of its effects on hemoglobin.

Methods: Prospective, single-arm study in CKD patients with ID and mild anemia. The 6-min walk test (6-MWT), Piper fatigue scale, Patient’s global assessment (PGA) and QoL (EQ-5D) questionnaires were evaluated at baseline, and at weeks 1 and 4 after receiving IV ferric carboxymaltose. Changes in continuous endpoints and their longitudinal trajectories were estimated with linear mixed regression models (LMRMs).

Results: Forty-one patients completed the study. The 6-MWT increased from 296±101 m to 314±106 m at week 1 (p<0.01), and to 325±111 meters at week 4 (p<0.01). PGA, EQ-5D questionnaire and Piper Fatigue scale significantly improved at week 4 from baseline (p<0.05), after adjustement in the last 2 variables. Hemoglobin levels did not increase significantly during the follow-up.

Conclusions: IV ferric carboxymaltose (IV FCM) was associated with a significant short-term improvement in the 6-MWT in CKD patients with iron deficiency and mild anemia. PGA, EQ-5D and Piper Fatigue Scale also improved at 4 weeks. These findings suggest a potential short-term benefit of IV ferric carboxymaltose on physical performance and PROMs in this population, independent of hemoglobin changes; however, given the small sample size and absence of a control group, results should be interpreted with caution and considered hypothesis-generating.