Intrinsic factor antibodies
| Category | Immunology |
|---|---|
| Test background |
Antibodies against Intrinsic Factor (IFAB) are present in 50-60% of patients with autoimmune atrophic gastritis, a chronic inflammatory condition resulting in the destruction of gastric parietal cells and subsequent loss of intrinsic factors (IF) and gastric acid. These are essential for the absorption of vitamin B12 from the intestine and their absence leads to vitamin B12 deficiency and megaloblastic anaemia. Pernicious anaemia can be a consequence of severe vitamin B12 deficiency but is now rare due to developments in testing and treatment. A negative IFAB does not rule out autoimmune gastritis. If clinical suspicion remains high NICE guidelines (NG239) recommend performing further tests which may include gastric parietal cell antibody (GPCA), gastrin levels, a CobaSorb test measuring vitamin B12 absorption and gastroscopy. This test is performed by ELISA and measures type 1 (blocking binding of vitamin B12 to IF) and type 2 (interfering B12-IF complex binding its receptor) IgG antibodies. |
| Clinical Indications |
Differential diagnosis of vitamin B12 deficiency. |
| Reference range | Negative |
| Sample & container required | Serum (RST rust top) |
| Sample volume | 5-10 mL blood (1 mL serum) |
| Turnaround time | 14 days |