Autoimmune gastritis is a chronic inflammatory condition where the body’s immune system mistakenly attacks healthy cells lining the stomach. This immune response primarily targets the parietal cells in the stomach, which produce stomach acid and intrinsic factor, a protein needed for vitamin B12 absorption. This article outlines the steps involved in its diagnosis.
Initial Patient Evaluation
Diagnosis of autoimmune gastritis begins with an initial patient evaluation. A healthcare provider will discuss the patient’s medical history, inquiring about existing autoimmune conditions, as autoimmune gastritis often co-occurs with disorders like Hashimoto’s thyroiditis or type 1 diabetes. Symptoms such as fatigue, unexplained weight loss, upper abdominal discomfort or pain, nausea, and early fullness after eating are also discussed.
A physical examination is also performed, where the doctor may check for abdominal tenderness. While these initial findings are often non-specific and can overlap with other gastrointestinal issues, they provide clues for further diagnostic tests. This initial step helps build a preliminary picture of the patient’s health.
Diagnostic Blood Tests
Blood tests play a significant role in diagnosing autoimmune gastritis, offering non-invasive insights into the body’s immune response and nutritional status. One primary test checks for parietal cell antibodies (PCAs), which are present in nearly all patients with chronic atrophic gastritis and a high percentage of those with pernicious anemia, a common outcome of autoimmune gastritis. These antibodies target the stomach’s acid-producing parietal cells.
Another specific test looks for intrinsic factor antibodies (IFAs). While PCAs are highly prevalent, IFAs are more specific to autoimmune gastritis, though found in a smaller percentage of patients (typically 40% to 80% in those with pernicious anemia). Given that autoimmune gastritis impairs vitamin B12 absorption, low serum vitamin B12 levels are a common finding. Individuals may also present with iron deficiency anemia due to impaired iron absorption, making iron level assessment a relevant part of the blood work. Serum gastrin levels are often elevated as a compensatory mechanism due to reduced stomach acid production from damaged parietal cells.
Endoscopy and Biopsy
Upper endoscopy (esophagogastroduodenoscopy or EGD), combined with a biopsy, is often considered the definitive method for diagnosing autoimmune gastritis. This procedure involves inserting a thin, flexible tube with a camera down the throat into the stomach, allowing direct visualization of the stomach lining. Tissue samples are collected from specific areas of the stomach, particularly the body and fundus, for microscopic examination.
Pathologists examine these tissue samples for characteristic histological findings that confirm autoimmune gastritis. These include glandular atrophy (thinning and loss of specialized glands in the stomach lining), and intestinal metaplasia (stomach cells replaced by intestine-like cells). The presence of inflammatory infiltrates, specifically lymphocytes and plasma cells, within the lamina propria of the stomach lining also points towards the condition. Enterochromaffin-like (ECL) cell hyperplasia, an increase in certain hormone-producing cells, may also be observed.
Ruling Out Other Conditions
Diagnosing autoimmune gastritis involves identifying its specific markers and differentiating it from other conditions with similar symptoms or endoscopic findings. Helicobacter pylori (H. pylori) infection is a common cause of gastritis and can lead to atrophic changes in the stomach lining, but its underlying mechanisms differ from autoimmune gastritis. While H. pylori gastritis often affects the antrum of the stomach more intensely, autoimmune gastritis primarily impacts the body and fundus.
Other forms of gastritis, such as reactive gastropathy caused by long-term use of NSAIDs or alcohol, also need to be considered. Symptoms like abdominal pain and weight loss can overlap with more serious conditions, including gastric cancer. The combination of clinical presentation, specific blood markers (parietal cell and intrinsic factor antibodies), and characteristic histological findings from the stomach biopsy helps accurately diagnose autoimmune gastritis and exclude look-alike conditions. This comprehensive approach ensures a precise diagnosis, guiding appropriate management and monitoring.