Iron resorption test

An iron absorption test (OIAT) is a laboratory-chemical functional test used to clarify an absorption disorder for iron (Herold 2018). It can be used to detect the permeability of the intestinal mucosa for bivalent iron (Hubl 2019).

Indication:

- Malabsorption for iron

- malabsorption

- hemochromatosis

- hemolytic anemia (Hubl 2019)

Test Procedure:

The patient appears fasting for testing. First, blood is drawn to determine serum iron. Then, the patient is given a drink containing 200 mg of absorbable divalent iron (e.g., with 2 capsules of Ferro Sanol duodenal [Hubl 2019]). After 2 - 4 - 8 hours, blood samples are taken again (Begemann 1999).

Hemolysis of the blood sample should be avoided at all costs (Hubl 2019).

Test result:

If iron absorption should be possible undisturbed, there is a strong increase in serum iron. After 2 h, a maximum is reached. Subsequently, the value drops again. In patients with an absorption disorder for iron, the increase does not occur (Begemann 1999).

Normally, the increase in serum iron is between 30 - 40% or 9 - 18 µmol / l (Hubl 2019).

Test interpretation:

• Intact intestinal absorption in:
  • normal baseline value for iron
  • Increase in serum iron by 30 - 40 %.
• Iron deficiency anemia with unimpaired intestinal absorption:
  • baseline iron value decreased
  • strong increase of serum iron by > 36 µmol / l
• Iron absorption disorder, malabsorption or infections:
  • baseline iron decreased
  • low increase in serum iron
• Hemochromatosis, hemolytic anemia:
  • Baseline iron increased
  • strong increase of serum iron (Hubl 2019)

The value of the iron absorption test is measured differently in the literature. According to Herold (2018), it is now rarely performed. It is not standardized (Gardyn 2021), is unsuitable for determining the cause of iron deficiency (Hubl 2019), and is only used to check the permeability of the intestine to divalent iron. The test does not reflect dietary iron intake (Hubl 2019). Lehmeyer (2017) refers to the OIAT as obsolete, whereas in "Harrison's Hematology and Oncology" it is described as useful in determining the ability of an iron absorption and to be able to treat accordingly (Longo 2017).

1. Begemann M (1999) Practical hematology: clinic, therapy, methodology. Georg Thieme Verlag Stuttgart / New York 665
2. Gardyn J, Chapal N, Floru S (2021) Oral iron absorption test: A simple test with relevance in the clinical setting. Isr Med Assoc J. 23 (10) 662 - 664
3. Hallbach J (2006) Clinical chemistry and hematology for beginners. Georg Thieme Verlag Stuttgart / New York 239 - 240.
4. Herold G et al (2018) Internal medicine. Herold Publ. 36
5. Hubl, W. (2019) Iron absorption test. In: Gressner, AM, Arndt, T. (Eds.) Encyclopedia of medical laboratory diagnostics. Springer Referenz Medizin Verlag Berlin, Heidelberg 757 https://doi.org/10.1007/978-3-662-48986-4_975.
6. Lehmeyer L, Stumpfe F (2017) Basics history and examination: hematology. Elsevier Health Service 48
7. Longo D L, Dietel M (2017) Harrison's hematology and oncology. ABW Science Publishers. Section 4 "Anemias"