Anti-parietal cell antibody (APCA) and Pernicious Anemia

Sample

1. Venous blood is needed to prepare the serum.
2. The serum of the patient is needed and should be stored at -20 c.
   • How to get good serum: Take 3 to 5 ml of blood in the disposable syringe or a vacutainer. Keep the syringe for 15 to 30 minutes at 37 °C and then centrifuge for 2 to 4 minutes to get the clear serum.

Indication

• This antibody test is done to diagnose the autoimmune type of Pernicious anemia.

Precaution

• APCA is present in many healthy persons over the age of 60 years.

Pathophysiology

5. The parietal cells are present in the proximal portion of gastric mucosa and produce acid (HCL) and Intrinsic factors.
6. The intrinsic factor is needed for the absorption of vit B 12.
   1. A lack of an intrinsic factor because of the antiparietal cells antibodies (APCA) will lead to pernicious anemia.
   2. These antiparietal cell antibodies lead to the destruction of the gastric mucosa.
      

      Parietal cells role in pernicious anemia and APCA

7. Parietal cell antibodies occur in patients with pernicious anemia (50 to 100 %).
8. There will be a disruption (no production) of the intrinsic factor by the parietal cells.
   1. In pernicious anemia, two types of antibodies were found:
      1. One against the parietal cells.
      2. Second, against the intrinsic factor.
         

         The autoantibodies destroy parietal cells.

         

         Parietal cells present in the upper portion of the stomach and produce Hcl and IF

         

         Antiparietal cell antibody formation (APCA)

         

         Pernicious anemia mechanism

9. This antibody can be seen in other autoimmune diseases (20 to 30%) like Thyroiditis, myxedema, juvenile diabetes, Addison disease, and iron-deficiency anemia.
10. Antiparietal cell antibodies are 95% positive in cases of Pernicious anemia (another reference says 76% to 91%).
    1. The normal population has 10 to 15 % of these antibodies.
       1. This is nonspecific to the IF antibody.
    2. With increasing age, the incidence of APCA increases, especially in the relatives of pernicious anemia patients.
    3. In autoimmune pernicious anemia, antiparietal antibodies are >80% positive; 50% have antibodies to intrinsic factor.
    4. Antiparietal antibodies are seen in healthy adults >60 years of age.
    5. Sometimes these antiparietal antibodies are seen in:
       1. Atrophic gastritis (idiopathic atrophic gastritis shows 30% to 60% APCA.
       2. Gastric ulcer.
       3. Gastric malignancies.
       4. Juvenile diabetes mellitus.
       5. Iron-deficiency anemia.
       6. Myxedema.
       7. Thyroiditis.
       8. Addison’s disease.
    6. APCA, when positive, then needs a more invasive procedure like a gastric biopsy to rule out a gastrointestinal disease.

Normal antiparietal cell antibodies:

• These are normally negative.

Source 4

• Negative antiparietal antibody by IFA technique.
  • When positive, then titrate the serum.
  • Positive = Titer level of 1:240

APCA is positive in:

1. Pernicious anemia (in 95% of the cases, although its specificity is low).
2. Atrophic gastritis (30% to 60%).
3. Gastric cancer and gastric ulcer.
4. These are present in 25 to 30% of the autoimmune diseases of the thyroid.
   1. Hashimoto’s thyroiditis (25%).
   2. Myxedema.
   3. Thyrotoxicosis (25% to 35%)
5. Juvenile diabetes (12% to 28%).
6. Addison disease.
7. Iron deficiency anemia.
8. A normal person (5% to 10%).

Increased level of APCA seen in:

1. Pernicious anemia.
2. Atrophic gastritis.
3. Myxedema.
4. Hashimoto’s thyroiditis.
5. Juvenile diabetes.
6. Addison disease.

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