Coombs Test: About This Test

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What is it?

A Coombs test is a type of antibody test. It checks your blood for certain antibodies that attack red blood cells. Antibodies are proteins made by the immune system. Normally, antibodies bind to foreign substances, such as bacteria and viruses, and cause them to be destroyed.

Why is this test done?

This test is used to:

  • Test blood before a transfusion.
  • Find antibodies caused by disease or a blood transfusion.
  • Check a newborn baby with Rh-positive blood whose mother has Rh-negative blood.
  • Check to see if a pregnant woman has Rh-positive or Rh-negative blood.

How can you prepare for the test?

  • In general, you don’t need to prepare before having this test. Your doctor may give you some specific instructions.

What happens during the test?

  • A health professional takes a sample of your blood.

What else should you know about the test?

  • Your results will include an explanation of what a "normal" result is. This is called a "reference range." It is just a guide. Your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed may still be normal for you.

How long does the test take?

  • The test will take a few minutes.

What happens after the test?

  • You will probably be able to go home right away.
  • You can go back to your usual activities right away.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

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