IV iron does not improve exercise capacity in iron-deficient kidney transplant recipients
Primary endpointBetween-group difference in 24-week change in 6-min walk test distance
Where these numbers come from
“Ferric carboxymaltose did not improve 6-min walk test distance versus placebo (adjusted mean difference +9 m [95% CI -10 to +28]).”
The publication
In a Dutch randomized trial, intravenous ferric carboxymaltose did not improve 6-minute walk test distance in iron-deficient kidney transplant recipients. The adjusted mean difference was +9 meters (95% CI -10 to +28) compared with placebo over 24 weeks.
Who the findings apply to
Adult kidney transplant recipients were eligible if they had iron deficiency, defined as ferritin below 100 μg/L or 100-299 μg/L with transferrin saturation below 20%.
Participants must have been at least six months post-transplantation and were recruited at two Dutch university hospitals.
Why this matters
The study addresses whether correcting iron deficiency enhances functional outcomes after transplantation. Although ferric carboxymaltose corrected iron deficiency and increased hemoglobin, it did not improve exercise capacity or other functional outcomes, arguing against routine supplementation to improve functional capacity.
What the study found
Ferric carboxymaltose did not improve 6-min walk test distance versus placebo, with an adjusted mean difference of +9 m (95% CI -10 to +28).
The intervention corrected iron deficiency and increased hemoglobin but did not improve cardiac function, muscle mass or strength, cognitive performance, or quality of life.
Exploratory between-group differences were observed in estimated glomerular filtration rate and fibroblast growth factor 23.
What the result does not establish
Infections and other clinically relevant adverse events did not differ between the ferric carboxymaltose and placebo groups.
The trial was a multicentre, double-blind, randomised, placebo-controlled study with 148 participants analyzed for efficacy.
Future studies are needed to investigate the observed differences in kidney function and fibroblast growth factor 23 concentrations and long-term clinical outcomes.
Authors’ conclusion
“Ferric carboxymaltose did not improve exercise capacity or most secondary outcomes, arguing against routine supplementation to improve functional capacity. Future studies should investigate observed differences in kidney function and fibroblast growth factor 23 concentrations and long-term clinical outcomes. Funding: Dutch Kidney Foundation, Dutch Heart Foundation, CSL Vifor.”
Study and sources
Intravenous ferric carboxymaltose and exercise capacity in iron-deficient kidney transplant recipients: a randomised, placebo-controlled trial in the Netherlands
Randomised trial · EClinicalMedicine · 2026-09-01
Sources and limitations
- PubMed record PMID 42733564 (PubMed / NLM · 2026-09-21)
- Trial registry NCT03769441 (ClinicalTrials.gov · 2026-09-21)
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