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Cholinesterase (Blood)

Does this test have other names?

RBC cholinesterase, true cholinesterase, red cell cholinesterase, acetylcholinesterase

What is this test?

This test looks for signs of chemical poisoning in your blood.

Cholinesterase is an enzyme that helps your nervous system work the way it should. Certain toxic chemicals in the environment can interfere with this enzyme and affect your nervous system.

These chemicals include organophosphates and carbamates. They are most often found in insecticides used in fields. They have also been used as chemical warfare agents. These chemicals can be found in common household insect sprays, too, such as Raid and Black Flag. They have been used in insecticides for more than 50 years.

If these chemicals get into your body, they can affect how you breathe and can cause general muscle weakness. They are called cholinesterase inhibitors. An overdose of these chemicals can be fatal.

Why do I need this test?

You may need this test if your healthcare provider thinks you have been overexposed to insecticides. Signs and symptoms of overexposure include:

  • Slow heart rate

  • Pupils in your eyes get smaller

  • You make more saliva than normal

  • You urinate more often than normal

  • You have trouble breathing

  • Watery eyes

  • Runny nose

  • Vomiting and diarrhea

These signs and symptoms vary, based on:

  • Your age

  • Amount of the overdose

  • What part of your body was exposed

  • Type of chemical

You may also have this test if you have symptoms of nervous system problems. These include:

  • Weakness when you bend your neck

  • Problems with the nerves in your neck

  • General muscle weakness

  • You aren’t able to breathe normally

This test is rarely used in an emergency because the results usually aren't available in time to suggest treatment. Instead, treatment of cholinesterase poisoning is usually based on symptoms.

What other tests might I have along with this test?

Your healthcare provider may also order other tests if you need treatment right away. These tests include:

  • Drug screen

  • Complete blood count, or CBC

  • Electrolyte panel

  • Blood culture

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.

The range of normal results varies greatly from lab to lab. But signs of poisoning start to appear in ranges that are 40% to 75% of normal.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Certain drugs can affect your results. These include birth control pills and medicines used to prevent malaria.

How do I get ready for this test?

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

Medical Reviewers:

  • Hanrahan, John, MD
  • Taylor, Wanda L, RN, PhD