12/10/2025
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When your doctor says you do not have pernicious anaemia because you are negative for intrinsic factor antibodies or that you cannot be deficient because your B12 is too high, you could show him/her this photo. Every area highlighted in blue could be the reason why you cannot absorb B12.
INTRINSIC FACTOR ANTIBODIES
Also known as: IFAb
Pernicious Anaemia is a clinical manifestation of autoimmune gastritis and is associated with the presence of intrinsic factor antibodies. There are two types of intrinsic factor antibody: type 1 binds to the vitamin B12 binding site and type 2 hinders the binding site by binding to structures nearby. Intrinsic factor antibodies are only performed in patients who are positive for gastric parietal cell antibodies.
New Guidelines for the diagnosis and treatment of cobalamin and folate disorders
All patients with anaemia, neuropathy or glossitis, and suspected of having pernicious anaemia, should be tested for anti-IFAB regardless of cobalamin levels (Grade 1A).
Patients found to have a low serum cobalamin level in the absence of anaemia and who do not have food malabsorption or other causes of deficiency, should be tested for IFAB to clarify whether they have an early/latent presentation of pernicious anaemia (Grade 2A).
Anti-GPC antibody testing for diagnosing pernicious anaemia is not recommended (Grade 1A).
GASTRIC PARIETAL CELL ANTIBODY
Also known as: GPC
Gastric parietal cell antibodies (GPC) are directed against a parietal cell enzyme, the H+K+ATPase. The auto-antibody is found at high frequency in association with autoimmune gastritis and a proportion of these patients will progress to develop pernicious anaemia.
Gastric parietal cell antibodies are present in over 90% of patients with pernicious anaemia (Highly sensitive, but not specific).
GPC antibodies should be looked for in:
Vitamin B12 deficiency
Macrocytic anaemia
Subacute combined degeneration of the cord
Individuals with other autoimmune disease i.e. thyroid disease
https://www.cmaj.ca/content/171/3/251
