Failure of CAPD patients to respond to an oral iron absorption test

CAPD patients require supplemental iron to maintain a response to erythropoietin. Because of limited availability of parenteral iron dextran, oral iron must be used. However, oral iron may not be effective in most dialysis patients. To determine if oral iron is well absorbed, a modified oral iron absorption or tolerance test was performed in CAPD patients using two oral iron preparations. Serum irons were measured at baseline in a fasting state and repeated two hours after the ingestion of 325 mgs ferrous sulfate in five CAPD patients. In addition, eight patients had serum irons determined before and two hours after taking liquid oral ferrous fumarate in capsule form. Healthy controls were compared with each group. All five patients who received ferrous sulfate had borderline to low normal serum iron and iron stores. Average increase in serum irons was only 19 mcg/dl in patients compared to 52 mcg/dl in controls. Patients receiving ferrous fumarate rose only 14 mcg/dl compared to 60 mcg/dl in controls. We conclude that oral iron is poorly absorbed in most CAPD patients and that the oral iron absorption test may be helpful in identifying patients who are effective iron absorbers. Unfortunately, until parenteral iron dextran is readily available, oral iron therapy is the only alternative for iron supplement. The oral iron absorption test may predict who will respond to oral iron in the long-term.