Parietal Cell Antibody
Also known as:Gastric Parietal Cell Antibody; Anti-parietal Cell Antibody; Anti-GPA; AGPA; APCA
Formal name:Gastric Parietal Cell Antibody, IgG
Related tests:Intrinsic Factor Antibody, Vitamin B12 and Folate, Methylmalonic Acid, Gastrin, Homocysteine, Complete Blood Count, Blood Smear
Why Get Tested?
To help diagnose pernicious anemia
When to Get Tested?
As part of an investigation, when you have anemia and/or neuropathy that may be due to a vitamin B12 deficiency; when you have red blood cells that are much larger than normal (macrocytic)
A blood sample drawn from a vein in your arm
Test Preparation Needed?
How is it used?
A parietal cell antibody test may be used along with or following an intrinsic factor antibody test to help determine the cause of a vitamin B12 deficiency and to help confirm a diagnosis of pernicious anemia.
It is usually used as a follow-up test after other laboratory tests, such as a vitamin B12 test, a methylmalonic acid test, or a complete blood count (CBC) with a blood smear examination, establish that a person has a vitamin B12 deficiency and associated megaloblastic anemia and/or neuropathy.
When is it ordered?
The parietal cell antibody test is not a frequently ordered test because it is not as specific as the intrinsic factor antibody test. It may be ordered when a person has signs and symptoms that suggest a vitamin B12 deficiency and when pernicious anemia is suspected. Signs and symptoms may include:
- Larger than normal red blood cells (RBCs); these are often detected before the other signs and symptoms emerge, found, for example, with a CBC during routine testing for a health examination.
- Weakness, fatigue
- Numbness and tingling in the feet and/or hands that may be due to neuropathy.
An intrinsic factor antibody test and parietal cell antibody test may be ordered as follow-up tests when a person has a decreased vitamin B12 level and increased methylmalonic acid and homocysteine levels.
What does the test result mean?
The results of this test are often taken into consideration with the results of other laboratory tests to help make a diagnosis. A decreased vitamin B12 level and/or increased methylmalonic acid and homocysteine levels as well as a positive test result for intrinsic factor antibodies and/or parietal cell antibodies means that it is likely that the person tested has pernicious anemia.
A negative test result does not necessarily mean that a person does not have pernicious anemia. At least 10% of those affected will not have parietal cell antibodies.
A positive test must be evaluated in the context of a person's other test results. Parietal cell antibodies are not as specific as intrinsic factor antibodies. About 90% of those with pernicious anemia will have parietal cell antibodies, but they may also be found in:
- Up to 50% of people with gastritis (inflammation of the stomach lining)
- Up to 30% of people with thyroiditis
- A variety of other conditions and autoimmune disorders
- A small percentage of the general population
The parietal cell antibody test is not used to diagnose or monitor these conditions.
Is there anything else I should know?
Vitamin B12-associated anemia may take several years to develop as a normal person typically has large stores of B12 in reserve. Symptoms tend to emerge only when these stores become depleted.
What is being tested?
Parietal cell antibodies are autoantibodies, proteins produced by the immune system that mistakenly target a type of specialized cells that line the stomach wall. This test detects these antibodies in the blood to help diagnose pernicious anemia.
Pernicious anemia can occur when the body's immune system targets its own tissues and develops antibodies directed against the parietal cells and/or the intrinsic factor. Intrinsic factor is a protein produced by the parietal cells and is required for the absorption of vitamin B12 from food. During digestion, stomach acids (also produced by parietal cells) release vitamin B12 from food, and intrinsic factor ultimately binds to the vitamin B12 and allows it to be absorbed at a specific segment of the small intestine. Among other functions, vitamin B12 is important in the production of red blood cells (RBCs). Without sufficient intrinsic factor, vitamin B12 goes largely unabsorbed and the body cannot produce enough normal RBCs, leading to anemia. Besides anemia, decrease in the numbers of neutrophils and platelets (neutropenia, thrombocytopenia) may also occur.
Parietal cells antibodies and other autoantibodies called intrinsic factor antibodies can disrupt intrinsic factor production or function. Both of these antibodies can lead to a decrease in the amount of intrinsic factor available, causing deficiency in vitamin B12.
Deficiency in vitamin B12 can lead to megaloblastic anemia, which is characterized by the production of fewer but larger RBCs called macrocytes. Several different factors can cause a B12 deficiency and result in megaloblastic anemia. When it is due to a lack of intrinsic factor, it is called pernicious anemia.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
- Can I prevent, decrease, or get rid of parietal cell antibodies?
No, they are produced by your immune system and do not respond to preventive measures or lifestyle changes. The associated vitamin B12 deficiency, however, can usually be successfully treated and managed.
- If I can't absorb vitamin B12, how can I get enough?
Periodic B12 injections can be given. If you are able to absorb some B12, then high doses of oral supplementation may help. You should consult with your health care provider for specific appropriate treatment options.
- Should everyone have a parietal cell antibody test?
It is not intended as a general screening test. It is usually only performed when a person has a demonstrated vitamin B12 deficiency to help determine the cause.
- Can I have a parietal cell antibody test done at my doctor's office?
This test requires specialized equipment and is not offered by every laboratory. In most cases, your blood will need to be sent to a reference laboratory.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
Descriptions of clinical laboratory tests were originally prepared for use on Lab Tests Online, an award-winning patient education website on clinical laboratory testing. Lab Tests Online is produced by the American Association for Clinical Chemistry (AACC), a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. The Lab Tests Online website is developed in collaboration with other laboratory professional societies and is funded in part through corporate sponsorships.