Albertine Donker

Chapter 4 190 Oral iron absorption test Method In order to evaluate the intestinal iron absorption, in five patients (two bi-allelic and three mono-allelic affected) an oral iron absorption test (OIAT) was performed. Three patients (ID 17, 19, 21) received one single dose of 400 mg ferrofumarate containing 130 mg ferrous iron. Serum iron was measured just before the administration of oral iron and after 30, 60, 90 and 120 minutes. No additional food intake was allowed. The physiological increase of serum iron in healthy individuals should be at least 15 µmol/L 120-180 minutes after oral intake of the test dose. 12 A fourth patient (ID 1), a child, received a challenge of 30 mg ferrofumarate containing 10 mg ferrous iron as an OIAT according to Gross, 13 who describes an average increase of 42 µmol/l after two hours in 10 iron replete individuals (five children, five adults) after a test dose of 1mg/kg ferrous iron. Patient ID 12, also a child, received a challenge of 80 mg ferrofumarate. Results In the bi-allelic patients 1 and 12 the increase of serum iron respectively 120 minutes and 90 minutes after oral administration of iron was 0 µmol/L. In the heterozygous patients 17, 19, and 21, this increase was 5.7, 1.3 and 12.2 µmol/L, respectively, and thus remained below the lower reference limit of 15 µmol/l. 12 Patients 19 and 21 were clinically responsive to oral iron in some extent ( Table 1, Supplemental Table 4 ), but had a very low oral iron absorption in the test while patient 17 was clinically unresponsive to oral iron and had a moderately low oral iron absorption in the test. From these experiments we conclude that the oral iron test was abnormal in all four IRIDA patients, especially in the homozygous affected patient. However, the quantitative results did not predict the severity of the phenotype and the response to oral iron in heterozygous patients. Ferrokinetic studies Method Before IRIDA had been diagnosed, in three patients (ID 3, 14, 15) ferrokinetic studies were performed in order to evaluate mucosal iron uptake, transfer, plasma iron clearance, red cell iron incorporation and iron retention. 14 To assess the kinetics of oral iron absorption a double isotope technique was used with 59 Fe as a tracer and 51 Cr as a non-absorbable indicator. With a whole body counter initial mucosal iron uptake and iron retention were measured and iron mucosal transfer was calculated. 14