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Exercise capacity in patients with chronic obstructive pulmonary disease (COPD) increased substantially following a single IV iron infusion, a researcher reported.

With patients' tolerance for physical activity measured with two standard assessments -- the 6-minute walk test (6MWT) and a constant work-rate exercise test -- more than half the patients receiving the infusion achieved the primary endpoint of at least a 33% improvement, compared with 18% of those given a placebo infusion (P=0.009)in a small, single-blind trial, said Clara Martin Ontiyuelo, of Hospital del Mar-IMIM in Barcelona, in a presentation at the European Respiratory Society virtual meeting.

That worked out to a relative risk of 3.12 (95% CI 1.19-8.12) for reaching the primary endpoint, her group calculated.

One secondary endpoint also favored the iron therapy, at least numerically: COPD Assessment Test scores, a patient-reported measure of quality of life, decreased a mean of 3.0 points (95% CI 1.3-6.0) with active treatment compared with a decline of 1.0 points (95% CI -2.3 to 4.0) in the placebo group (P=0.236). There was no difference in daily physical activity or in adverse events, Martin Ontiyuelo said.

She explained that iron deficiency is a and, of course, can negatively affect exercise ability. That suggests a potential role for supplementation in iron-deficient patients.

Her group is not the first to come to this conclusion. An even smaller trial in Germany was , though whether it began or was completed couldn't be determined. Another small study conducted in Great Britain with IV iron was ; it found no improvement in blood oxygenation but, as in the Barcelona trial, 6MWT distance was lengthened with the active supplement.

All three used a ferric carboxymaltose product (Ferinject) for the infusion. Martin Ontiyuelo explained that, at least for her group, the choice was based on "logistical issues, as a single dose shows interesting and fast effects." Oral iron, she said, often has poor absorption and isn't always well tolerated.

Her group's trial, , randomized 66 patients at a 2:1 ratio to the iron infusion or placebo. Patients had to show iron deficiency defined as either serum ferritin less than 100 ng/mL, or 100-299 ng/mL with coexisting transferrin saturation less than 20%. Patients did not need to show overt anemia, however.

The exercise tolerance tests were performed at baseline and again at 4 weeks following the infusion. Patients wore accelerometers during this follow-up period to measure physical activity. Dosage for the iron infusion was either 500 or 1,000 mg, according to patients' weight and baseline hemoglobin level.

In her presentation, Martin Ontiyuelo did not mention how much patients' iron levels improved with the infusions. When an online audience member asked about it afterward, she responded that there was "an important change in ferritin" that her group would report in detail as part of a forthcoming publication.

She also said there were no allergic reactions to the iron infusion.

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