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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Gastroenterology

How Autoimmune Gastritis is Diagnosed

At a Glance

Diagnosing autoimmune gastritis requires a three-step approach: blood tests to check for specific antibodies and stomach function markers, an endoscopy to visually inspect the stomach lining, and a tissue biopsy using the Sydney System to confirm microscopic changes like atrophy.

Because Autoimmune Gastritis (AIG) can mimic other conditions, doctors use a “multimodal” approach to confirm the diagnosis [1]. This means they look at three different types of evidence: your blood work (serology), the visual appearance of your stomach (endoscopy), and the microscopic analysis of your tissue (histology) [2][3].

Phase 1: The Blood Tests (Serology)

Blood markers are often the first step in identifying AIG. These tests look for both the presence of the immune attack and the resulting loss of stomach function.

  • Autoantibodies: The most common tests look for Anti-Parietal Cell Antibodies (APCA) and Anti-Intrinsic Factor Antibodies (AIFA) [4]. While APCA is very common in early AIG, these levels can actually drop as the disease progresses because there are fewer parietal cells left for the immune system to attack [5][6]. AIFA is a more specific marker and is a strong warning sign for Pernicious Anemia [7].
  • Stomach Function Markers:
    • Gastrin-17: When the stomach cannot produce acid, it sends a signal to produce more gastrin to compensate. In AIG, gastrin levels are typically very high [8].
    • Pepsinogen I and II: These are proteins produced by the stomach lining. A low level of Pepsinogen I or a low Pepsinogen I/II ratio is a reliable sign that the stomach lining is thinning (atrophy) [8][9].

Phase 2: The Camera (Endoscopy)

During an endoscopy, a gastroenterologist looks for specific visual clues. In AIG, the damage is typically corpus-restricted, meaning it is found in the main body of the stomach while the lower part (the antrum) remains healthy [10].

Key visual signs include:

  • Patchy Atrophy: Areas where the stomach lining looks thin or pale [11].
  • Loss of Gastric Folds: The normal “wrinkles” in the stomach lining may appear flattened [12].
  • Gyrus-like Changes: Patterns that may look like the surface of the brain on the stomach wall [11].

Phase 3: The Microscope (Histology)

The “gold standard” for diagnosis is the biopsy, where tiny tissue samples are examined by a pathologist [1]. For a complete picture, doctors should follow the Sydney System, which involves taking at least five biopsies from different parts of the stomach [13].

Pathologists look for:

  • Metaplasia: When the stomach lining begins to transform into a different type of tissue (like intestinal or pyloric tissue) to survive the immune attack [2].
  • ECL-Cell Hyperplasia: An overgrowth of certain cells caused by high gastrin levels. This is a key feature that distinguishes AIG from other types of gastritis [14].
  • Atrophy Staging: Doctors use systems like OLGA (for atrophy) and OLGIM (for metaplasia) to grade the severity of the damage [15][16].

Your Pathology “Completeness Checklist”

When you receive your pathology report, look for these key details to ensure a thorough evaluation:

    • Biopsy Location: Samples taken from both the corpus (top/middle) and antrum (bottom).
    • H. pylori Status: A definitive “negative” for active infection [17].
    • Atrophy Grade: Mention of OLGA or OLGIM staging (e.g., Stage I-IV) [15].
    • Specialized Cells: Comments on ECL-cell status (e.g., “hyperplasia” or “linear/micronodular”) [14].
    • Inflammation Pattern: Description of where the inflammation is centered (ideally the corpus for AIG) [10].
Marker Typical Result in AIG What it Means
APCA / AIFA Positive Immune system is attacking stomach cells.
Gastrin High Stomach is trying to compensate for low acid.
Pepsinogen I/II Low Significant thinning/loss of stomach lining.
H. pylori Negative Rules out the most common non-autoimmune cause.

Common questions in this guide

What blood tests are used to diagnose autoimmune gastritis?
Doctors look for anti-parietal cell antibodies (APCA) and anti-intrinsic factor antibodies (AIFA) to see if your immune system is attacking your stomach. They also measure gastrin and pepsinogen levels to evaluate how well your stomach is functioning.
Why do I need an endoscopy for autoimmune gastritis?
An endoscopy allows a gastroenterologist to visually inspect your stomach lining for signs of damage. In autoimmune gastritis, they specifically look for patchy thinning, flattened gastric folds, and changes restricted to the main body of the stomach.
What is the Sydney System for stomach biopsies?
The Sydney System is the standard protocol for taking stomach biopsies during an endoscopy. It requires doctors to take at least five tissue samples from different parts of the stomach to ensure no areas of damage or inflammation are missed.
What does ECL-cell hyperplasia mean on my pathology report?
ECL-cell hyperplasia refers to an overgrowth of certain stomach cells caused by high gastrin levels. This overgrowth is a key characteristic that helps pathologists distinguish autoimmune gastritis from other types of stomach inflammation.
What are the OLGA and OLGIM staging systems?
OLGA and OLGIM are grading systems used by pathologists to determine the severity of damage in your stomach lining. They measure the extent of cell loss and tissue transformation to help doctors understand the progression of your condition.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Did we perform the 'five-biopsy protocol' (Sydney System) to ensure we sampled all areas of my stomach?
  2. 2.Does my pathology report mention 'ECL-cell hyperplasia' or 'pseudopyloric metaplasia'?
  3. 3.What was my OLGA or OLGIM stage, and how does that affect my risk for future complications?
  4. 4.If my anti-parietal cell antibody test was negative but my gastrin is high, does that mean my disease is in an advanced stage?
  5. 5.Was H. pylori infection definitively ruled out during my biopsy or through other testing?

Questions For You

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Related questions

Can Autoimmune Gastritis Have Negative Antibodies?Is Autoimmune Gastritis Deadly? Risks & Life ExpectancyWhat Do High Gastrin Levels Mean in Autoimmune Gastritis?What is the Prognosis for Autoimmune Gastritis?

References

References (17)
  1. 1

    A case of nodular gastritis progression to autoimmune gastritis after 10 years of Helicobacter pylori eradication.

    Sumi N, Haruma K, Inoue K, et al.

    Clinical journal of gastroenterology 2024; (17(2)):216-221 doi:10.1007/s12328-023-01897-5.

    PMID: 38072907
  2. 2

    Autoimmune gastritis: long-term natural history in naïve Helicobacter pylori-negative patients.

    Rugge M, Bricca L, Guzzinati S, et al.

    Gut 2023; (72(1)):30-38 doi:10.1136/gutjnl-2022-327827.

    PMID: 35772926
  3. 3

    Update in Molecular Aspects and Diagnosis of Autoimmune Gastritis.

    Iwamuro M, Tanaka T, Otsuka M

    Current issues in molecular biology 2023; (45(7)):5263-5275 doi:10.3390/cimb45070334.

    PMID: 37504250
  4. 4

    A comparative study of different assays for autoantibodies detection in patients with autoimmune gastritis.

    Osmola M, Hémont C, Romańczyk M, et al.

    Journal of translational autoimmunity 2025; (10()):100294 doi:10.1016/j.jtauto.2025.100294.

    PMID: 40519797
  5. 5

    Letter to the editor commenting on 'decreased anti-parietal cell antibody titer in the advanced phase of autoimmune gastritis' by Nishizawa et al.

    Guo X, Schreurs MWJ, Doukas M, et al.

    Scandinavian journal of gastroenterology 2023; (58(7)):838-839 doi:10.1080/00365521.2023.2174816.

    PMID: 36734401
  6. 6

    Decreased anti-parietal cell antibody titer in the advanced phase of autoimmune gastritis.

    Nishizawa T, Watanabe H, Yoshida S, et al.

    Scandinavian journal of gastroenterology 2022; (57(2)):143-148 doi:10.1080/00365521.2021.1994642.

    PMID: 34693845
  7. 7

    Clinicopathological characteristics of autoimmune gastritis: A single-center retrospective study.

    Wang X, Lu CJ, Li H, et al.

    Clinics and research in hepatology and gastroenterology 2023; (47(7)):102154 doi:10.1016/j.clinre.2023.102154.

    PMID: 37311519
  8. 8

    Relevance of pepsinogen, gastrin, and endoscopic atrophy in the diagnosis of autoimmune gastritis.

    Kishikawa H, Nakamura K, Ojiro K, et al.

    Scientific reports 2022; (12(1)):4202 doi:10.1038/s41598-022-07947-1.

    PMID: 35273265
  9. 9

    Autoimmune Gastritis Complicated by Primary Biliary Cholangitis: A Report of Two Cases and Literature Review.

    Toyoda M, Ichikawa M, Nakamura K, et al.

    Cureus 2025; (17(3)):e80208 doi:10.7759/cureus.80208.

    PMID: 40190954
  10. 10

    Differences in image-enhanced endoscopic findings between Helicobacter pylori -associated and autoimmune gastritis.

    Kato M, Uedo N, Toth E, et al.

    Endoscopy international open 2021; (9(1)):E22-E30 doi:10.1055/a-1287-9767.

    PMID: 33403232
  11. 11

    Mucosal Atrophy of the Fornix as an Important Endoscopic Finding for an Autoimmune Gastritis Diagnosis.

    Adachi K, Okimoto E, Ebisutani Y, et al.

    Internal medicine (Tokyo, Japan) 2026; (65(1)):88-95 doi:10.2169/internalmedicine.5638-25.

    PMID: 40500167
  12. 12

    An Evaluation of Endoscopic Images from Over 15 Years Prior to the Diagnosis of Autoimmune Gastritis: A Report of Three Patients.

    Ayaki M, Manabe N, Murota M, et al.

    Internal medicine (Tokyo, Japan) 2022; (61(6)):827-833 doi:10.2169/internalmedicine.8178-21.

    PMID: 34483214
  13. 13

    Clue of Diagnosis for Autoimmune Gastritis.

    Nishizawa T, Yoshida S, Watanabe H, et al.

    Digestion 2021; (102(6)):903-910 doi:10.1159/000516624.

    PMID: 34198294
  14. 14

    Features That Aid Identification of Autoimmune Gastritis in a Background of Active Helicobacter pylori Infection.

    Choudhuri J, Hall S, Castrodad-Rodriguez CA, et al.

    Archives of pathology & laboratory medicine 2021; (145(12)):1536-1543 doi:10.5858/arpa.2020-0615-OA.

    PMID: 33635965
  15. 15

    Gastritis staging as a clinical priority.

    Mescoli C, Gallo Lopez A, Taxa Rojas L, et al.

    European journal of gastroenterology & hepatology 2018; (30(2)):125-129 doi:10.1097/MEG.0000000000001015.

    PMID: 29215433
  16. 16

    Autoimmune gastritis may be less susceptible to cancer development than Helicobacter pylori-related gastritis based on histological analysis.

    Arai J, Niikura R, Hayakawa Y, et al.

    Gut 2024; (73(6)):1037-1038 doi:10.1136/gutjnl-2023-330052.

    PMID: 37197906
  17. 17

    Helicobacter pylori Gastritis as an Initial Presentation of Evolving Autoimmune Gastritis: A Report of Two Cases.

    Kotera T, Kushima R, Haruma K

    Internal medicine (Tokyo, Japan) 2026; (65(6)):819-826 doi:10.2169/internalmedicine.5888-25.

    PMID: 40769905

This page explains the diagnostic process and pathology terminology for autoimmune gastritis for educational purposes. Always consult your gastroenterologist or pathologist for interpreting your specific test results.

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