Anti–Parietal Cell Antibodies (APC)

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Subject: Anti–Parietal Cell Antibodies (APC)

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Definition

  • Antibodies to gastric parietal cells that react with the cell membrane, cytoplasmic antigens, or gastric intrinsic factor are present in essentially all (>90%) of individuals with pernicious anemia. In 70% of patients, antibodies reactive with the vitamin B12–binding site of intrinsic factor are present, and in 50% of patients, additional antibodies are present, which react with a second antigenic site on the 44,000-Da intrinsic factor protein molecule. These autoantibodies lead to a pathologic immune process termed “chronic autoimmune gastritis,” which may slowly progress for 10–20 years and finally terminate in gastric atrophy. The gastric atrophy results in a lack of absorption of vitamin B12 and leads to megaloblastic anemia in patients with anti–parietal cell antibodies. Pernicious anemia is associated with a variety of other autoimmune diseases including thyrotoxicosis, Hashimoto thyroiditis, insulin-dependent DM, primary Addison disease of the adrenals, primary ovarian failure, primary hypoparathyroidism, vitiligo, Myasthenia gravis, and the Lambert-Eaton syndrome.

  • Normal range:

    • IFA: negative; if positive, results are tittered, ELISA: <1:40 titer.

    • APC titers greater than 1:40 are significant.

Use

  • Aids in the evaluation of patients suspected of having pernicious anemia

  • Evaluation of immune-mediated deficiency of vitamin B12 with or without megaloblastic anemia

Interpretation

Increased In

  • Pernicious anemia

  • Atrophic gastritis

  • Diabetes

  • Gastric ulcer

  • Thyroid disease

Decreased In

  • NA

Limitations

  • High blood levels are also seen in people with inflammation of the lining of the stomach, stomach ulcers, and stomach cancer.

  • APC antibodies may occur with increased frequency in unaffected family members, a small percentage of healthy individuals, and patients with other autoimmune diseases, such as autoimmune thyroiditis.

 
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