Anti-Parietal Cell Antibody (APCA)

Antibodies against the cells that make stomach acid. They are linked to autoimmune gastritis and pernicious anemia, but also appear in people who have neither.

AI-verified against cited sources. Awaiting expert reviewAlso called APCALOINC 40960-7

What it is

Parietal cells line your stomach. They make acid and a protein called intrinsic factor that your body needs to absorb vitamin B12. In autoimmune gastritis, the immune system makes antibodies that target an acid pump on these cells. This test measures those antibodies. Labs report either an immunofluorescence titer or a number from an ELISA, and each has its own cutoff.

Why it matters

This test is mostly used to look for a reason behind low vitamin B12, iron deficiency or anemia. The antibodies are found in about 90% of people with pernicious anemia, which is a form of vitamin B12 deficiency caused by autoimmune gastritis. They are not very specific, though, and they also appear in some people with other autoimmune conditions and in a few healthy people. A negative result makes autoimmune gastritis unlikely, but a positive result on its own does not confirm it.

If it’s high

A result above your lab's cutoff is reported as positive. It means the immune system is reacting to stomach acid cells, which is linked to autoimmune gastritis and pernicious anemia. It does not tell you whether your stomach lining is damaged or whether your vitamin B12 is low. Many people with a positive result do not have gastritis on biopsy.

Common causes

No stomach disease at all: the antibodies appear in a small percentage of healthy people and in some relatives of people with the condition
Another autoimmune condition, such as autoimmune thyroid disease
Stomach inflammation from Helicobacter pylori infection
Autoimmune gastritis, with or without pernicious anemia

What can help

Ask whether vitamin B12, folate, iron studies and a blood count should be checked
Ask whether an intrinsic factor antibody test would add information, since it is more specific for pernicious anemia
Ask whether a stomach exam with biopsies is needed to look at the stomach lining
Tell your clinician about any other autoimmune conditions you or your family have

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 0–20 Units. Source: ARUP Laboratories, UI Health Care (University of Iowa Hospitals & Clinics) Laboratory Services Handbook.

Adults (this one applies)0–20 Units
Sources: ARUP Laboratories, UI Health Care (University of Iowa Hospitals & Clinics) Laboratory Services Handbook

What can affect your result

Age: antibody levels decline with age, so a negative result is less reliable in older adults
H. pylori infection can raise levels, and levels may fall after it is treated
Other autoimmune conditions, such as autoimmune thyroid disease, make a positive result more common
Family history: relatives of people with pernicious anemia are more often positive
Test method: immunofluorescence titers and ELISA units use different scales and cutoffs
Immunofluorescence titers and ELISA units are different scales with different cutoffs, so results from different labs cannot be compared directly.
H. pylori infection can raise the antibody level, and levels can fall after the infection is treated.
Levels decline with age, so a negative result is less reliable in older adults.
ARUP rejects plasma, urine and samples that are contaminated, heat-inactivated, grossly hemolyzed or severely lipemic for this test.

When to talk to a clinician

A positive result is not urgent by itself. Talk with a clinician if you have it along with unusual tiredness, paleness, shortness of breath, numbness or tingling in the hands or feet, trouble with balance, or memory changes, since these can go with low vitamin B12.

Questions you could ask

Why was this test ordered, and what will we do with the result?
Should my vitamin B12, iron and blood count be checked?
Would an intrinsic factor antibody test or a stomach exam help?
Does this result matter for my other autoimmune conditions?

Questions people ask

Does a positive result mean I have pernicious anemia?

No, not by itself. Many people with positive parietal cell antibodies do not have pernicious anemia or gastritis. Your clinician will look at your vitamin B12, blood count and sometimes an intrinsic factor antibody test or a stomach exam.

Can I have autoimmune gastritis with a negative result?

It is possible but uncommon. In one review, if about 3 in 100 people have the condition, a negative result was right about 99 times out of 100. Levels also fall with age, so a negative result is less reliable in older adults.

Why do labs report titers or units?

Some labs use immunofluorescence and report a titer such as 1:80, and others use an ELISA and report a number in arbitrary units. The scales and cutoffs differ, so compare your result with the range printed on your own report.

Show the science and sources

For clinicians and researchers

Parietal cell antibodies target the H+/K+ ATPase (proton pump) of gastric parietal cells and are a serologic marker of autoimmune gastritis, found in 60-90% of patients with autoimmune atrophic gastritis (Cancers 2024) and in about 90% of patients with pernicious anemia, but with low specificity: they also occur in atrophic gastritis without megaloblastic anemia and in various autoimmune disorders (Autoimmun Rev 2014). Intrinsic factor antibodies are far more specific but less sensitive (about 60% of pernicious anemia). For autoimmune atrophic gastritis, one review reports APCA sensitivity 81% and specificity 90%; at a 3% prevalence that gives a negative predictive value of 99% and a positive predictive value of about 20%. The same review describes 'potential' autoimmune gastritis (positive APCA without atrophy on biopsy), with about 10.9% a year progressing to overt disease in one prospective study, notes that APCA decline with age, and notes that levels are high in H. pylori-positive corpus atrophic gastritis and fall after eradication (Cancers 2024). The AGA 2021 clinical practice update advises considering APCA and anti-intrinsic factor antibody testing in patients whose histology fits autoimmune gastritis, along with an evaluation for anemia from B12 and iron deficiency, and says the diagnosis of atrophic gastritis should be confirmed by histopathology. ARUP Consult notes that APCA are more sensitive than intrinsic factor antibodies but less specific, and states that a positive APCA after a negative intrinsic factor test, in the appropriate clinical context, confirms the diagnosis of pernicious anemia. ARUP's ELISA reports arbitrary Units (0.0-20.0 negative, 20.1-24.9 equivocal, 25.0 or more positive; reference interval 24.9 or less) and notes that the antibodies are found with increased frequency in unaffected family members, in a small percentage of healthy individuals and in autoimmune thyroiditis. Immunofluorescence titers and ELISA units differ by lab and kit.

LOINC 40960-7 (primary), 27320-1, 5271-2, 56147-2, 14241-4. Specimen: serum.

Sources

Gastric Parietal Cell Antibody, IgG (test 0050596), ARUP Laboratories
Megaloblastic Anemia, ARUP Consult
Diagnosis and classification of pernicious anemia, Autoimmunity Reviews (2014)
Autoimmune Atrophic Gastritis: A Clinical Review, Cancers (Basel) (2024)
AGA Clinical Practice Update on the Diagnosis and Management of Atrophic Gastritis: Expert Review, Gastroenterology (2021)
Parietal Cell Antibodies, IgG, UI Health Care (University of Iowa Hospitals & Clinics) Laboratory Services Handbook

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.