Intrinsic Factor Antibody

Does this test have other names?

IF antibody; intrinsic factor antibody level; intrinsic factor blocking antibody measurement; antibody level, intrinsic factor

What is this test?

This is a blood test for pernicious anemia, which is caused by a deficiency of vitamin B-12. The disease used to be life-threatening, but today it can be treated with vitamin B-12 shots or pills.

To get enough vitamin B-12, your body needs a protein called intrinsic factor (IF). This protein is made by your stomach lining. It allows you to absorb vitamin B-12 from the food you eat. Your body needs B-12 to make healthy red blood cells within your bone marrow. If you don't get enough B-12, your red blood cells won't divide correctly and will be too large, making it hard for them to squeeze out of the bone marrow. This can lead to anemia, or a lack of red blood cells. Without enough B-12, your nervous and digestive systems also won't work correctly.

The body produces antibodies to attack what it believes to be foreign substances. If your body sees IF as a foreign invader and makes antibodies against it, IF will be destroyed and can't help your body absorb vitamin B-12.

Why do you need this test?

You may need this test if your health care provider believes you have pernicious anemia or a vitamin B-12 deficiency. Symptoms of anemia include:

• Paleness.

• Tiredness.

• Weakness.

• Tingling and numbness in the hands and feet, or a "pins and needles" feeling (neuropathy).

What other tests might you have along with this test?

As part of your diagnosis for pernicious anemia, you may need a vitamin B-12 test or a folate level test to measure the amount of the vitamin in your blood. You may also order tests to check the levels of homocysteine and methylmalonic acid. If your levels of these are high (elevated), it may suggest pernicious anemia.

To help confirm the diagnosis, you may need an antiparietal cell antibody test. This measures the presence of certain antibodies in the stomach.

What do your test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your health care provider what your test results mean for you.

Test results that are negative for the presence of IF antibody are considered normal. But it's possible to have pernicious anemia in spite of this negative test result.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What might affect your test results?

Injected vitamin B-12 could affect results. If you have had an injection of this vitamin, your health care provider will likely ask you to wait for at least 48 hours and possibly up to 2 weeks before testing.

How do you get ready for this test?

You don't need to prepare for this test. Be sure your health care provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.