Intrinsic factor Antibody (IF Ab)
- The serum the patient is needed.
- This test can also be done on the plasma.
- The sample is stable for 4 hours at room temp.
- By refrigerating the sample is stable for 3 days.
Purpose of the test (Indication)
- To diagnose the pernicious anemia.
- Avoid injection of vit.B12 within 48 hours of testing.
- Megaloblastic anemia is due to a deficiency of vit.B12 which is the major cause.
- Intrinsic factor is secreted in the stomach and this is needed for the absorption of the vit.B12.
- The intrinsic factor is the protein produced by the parietal cells.
- Antibodies against the intrinsic factor are produced by the activation of the immune system.
- In Megaloblastic anemia IF is decreased or absent.
- This is one of the autoimmune diseases.
- IF Ab is found in the high percentage of the children with juvenile pernicious anemia.
- IF Ab is 50 to 75% positive in these patients.
- IF Ab is of two types :
- Blocking Ab which is more common, blocks the binding of vit.B12 to IF.
- The binding antibody which binds with the site on the intrinsic factor.
- The second antibody is less common which affects the binding of IF in the ileum.
- Positive IF Ab is confirmatory and is the cause of the disease.
- Negative IF Ab does not rule out megaloblastic anemia because 50% of the patient does not show this antibody.
- For the diagnosis of Pernicious anemia, can supplement IF Ab with an anti-parietal antibody test.
- Pernicious anemia rarely needs the vit.B12 absorption test called the Schilling test.
- The testing of the intrinsic factor antibody and the anti-parietal antibodies is easier, quick, and more accurate.
- Intrinsic factor antibody = Negative.
- Increased IF Ab is seen in a patient with pernicious anemia.
- The IF antibodies are present in 3 to 6% of hyperthyroidism and insulin-dependent diabetes.