What are the diagnostic criteria and treatment options for autoimmune gastritis?

Diagnosis of Autoimmune Gastritis

The diagnosis of autoimmune gastritis requires histopathological confirmation through endoscopic biopsies, along with serological testing for antiparietal cell antibodies (PCA) and anti-intrinsic factor antibodies (IFA). 1

Diagnostic Criteria

Histopathological Assessment (Gold Standard)

• Endoscopic features to recognize:

  • Pale appearance of gastric mucosa
  • Increased visibility of vasculature due to mucosal thinning
  • Loss of gastric folds
  • Corpus-predominant pattern with antral sparing 1

• Biopsy protocol:

  • Obtain biopsies from suspected atrophic/metaplastic areas
  • At minimum, collect samples from both body and antrum/incisura in separately labeled containers
  • Target any additional mucosal abnormalities 1

• Histological findings:

  • Oxyntic mucosa atrophy with lymphoplasmacytic infiltrate
  • Loss of gastric glands in corpus/fundus
  • Intestinal metaplasia (often present) 1, 2

Serological Testing

• Autoantibody testing:

  • Antiparietal cell antibodies (PCA) - highly sensitive but less specific
  • Anti-intrinsic factor antibodies (IFA) - highly specific but less sensitive 1, 3

• Markers of gastric corpus atrophy:

  • Elevated serum gastrin (due to hypochlorhydria)
  • Decreased pepsinogen I levels
  • Decreased pepsinogen I/II ratio 3

Associated Testing

Micronutrient Deficiency Evaluation

• Vitamin B12 assessment:

  • Serum B12 levels
  • Methylmalonic acid and homocysteine (more sensitive markers of B12 deficiency) 1, 2

• Iron status evaluation:

  • Complete blood count
  • Serum iron, ferritin, and transferrin saturation 1, 4

Helicobacter pylori Testing

• All patients should be tested for H. pylori infection
• Use non-serological testing methods:
  • Urea breath test
  • Stool antigen test
  • Histological examination with special stains 1, 5

Screening for Associated Autoimmune Conditions

• Thyroid function tests (highest association with autoimmune thyroid disease)
• Consider screening for other autoimmune conditions based on clinical presentation:
  • Type 1 diabetes
  • Vitiligo
  • Addison's disease
  • Celiac disease 1, 6

Clinical Presentations That Should Prompt Testing

1. Hematologic manifestations:

   • Unexplained iron deficiency anemia
   • Vitamin B12 deficiency/pernicious anemia
   • Macrocytic anemia 1, 2, 6

2. Neurological symptoms:

   • Paresthesias
   • Ataxia
   • Cognitive impairment 7, 6

3. Gastrointestinal symptoms:

   • Dyspepsia
   • Reflux symptoms (though often asymptomatic) 2, 4

4. Comorbid autoimmune disorders:

   • Particularly autoimmune thyroid disease
   • Celiac disease
   • Type 1 diabetes 1, 6

Management Considerations

• Micronutrient replacement:

  • Vitamin B12 supplementation (parenteral if pernicious anemia present)
  • Iron supplementation if deficient 1, 2

• Surveillance for neoplastic complications:

  • Endoscopic surveillance every 3 years for advanced atrophic gastritis
  • Individualized surveillance intervals for autoimmune gastritis based on risk assessment
  • Screening for type 1 gastric neuroendocrine tumors (NETs) 1

• Management of NETs:

  • Small NETs should be removed endoscopically
  • Follow-up surveillance every 1-2 years depending on tumor burden 1, 5

Common Pitfalls to Avoid

• Failure to recognize atrophic gastritis: Intestinal metaplasia on gastric histology almost invariably implies the diagnosis of atrophic gastritis 1

• Inadequate biopsy sampling: Biopsies must include both corpus and antrum/incisura in separate containers 1

• Overlooking micronutrient deficiencies: Test for iron and vitamin B12 deficiencies even in the absence of anemia 1, 4

• Missing associated autoimmune conditions: Screen for autoimmune thyroid disease and consider other autoimmune disorders 1, 6

• Inadequate H. pylori testing: Use non-serological testing methods and confirm eradication if positive 1, 5