title: Reference values for oral iron absorption of bivalent iron in healthy volunteers.
abstract: BACKGROUND
  It is a challenge to establish the cause of iron deficiency in the absence of obvious reasons. There has been no prospectively validated oral iron absorption test (OIAT) that could confidently confirm or exclude iron malabsorption. The aim, therefore, was the establishment of an OIAT with defining reference values of plasma iron in healthy volunteers.
  
  
  METHODS
  We included 49 healthy volunteers who received 200 mg of bivalent ferrous fumarate in fasting condition and measured plasma iron after 2 and 4 hours as well as after 3 and 5 days. After a wash-out phase, 23 healthy volunteers proceeded to receive trivalent iron hydroxide polymaltose in fasting condition, and 11 participants were tested without iron.
  
  
  RESULTS
  Reference values of absolute and relative plasma iron after oral iron ingestion could be established. There was a significant increase of plasma iron after bivalent iron intake within 4 hours after ingestion (absolute increase after 4h: from initially 17 ± 4 µmol/l to 35 ± 12 µmol/l in females and from 21 ± 7 µmol/l to 33 ± 11 µmol/l in males, relative plasma iron concentration (defined reference: 1.0) after 4 h: 2.1 ± 0.7 in females and 1.7 ± 0.6 in males). There was no relevant increase with trivalent iron nor without iron. Relative iron increase correlates to iron storage. In general, females had lower ferritin levels and thus higher increases of plasma iron.
  
  
  CONCLUSIONS
  An OIAT in healthy volunteers could be established. Its prospective validation using bivalent iron in iron deficiency is desirable.
authors.affiliation: Division of Haematology and Central Haematology Laboratory, Department of Medicine, Luzerner Kantonsspital, Switzerland.
authors.forename: Korinna
authors.initials: K
authors.lastname: Kloepfer
authors.affiliation: Division of Haematology and Central Haematology Laboratory, Department of Medicine, Luzerner Kantonsspital, Switzerland.
authors.forename: Pirmin
authors.initials: P
authors.lastname: Schmid
authors.affiliation: Division of Haematology and Central Haematology Laboratory, Department of Medicine, Luzerner Kantonsspital, Switzerland.
authors.forename: Walter A
authors.initials: WA
authors.lastname: Wuillemin
authors.affiliation: Division of Haematology and Central Haematology Laboratory, Department of Medicine, Luzerner Kantonsspital, Switzerland.
authors.forename: Axel
authors.initials: A
authors.lastname: Rüfer
mesh_terms: D000284:Administration, Oral; D000328:Adult; D005260:Female; D005290:Ferric Compounds / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D005296:Ferrous Compounds / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D064368:Healthy Volunteers; D006801:Humans; D007501:Iron / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013997:Time Factors
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D007501:Iron; C031621:ferrous fumarate; C013276:teferrol