Back Blood-tests Explained


Cholinesterase


At a Glance

Why Get Tested?

  • To determine if you have been exposed to and/or poisoned by certain organophosphate chemicals found in pesticides; to monitor cholinesterase levels if you work with pesticides
  • Sometimes to identify individuals with inherited pseudocholinesterase deficiency before they are given anesthesia with the muscle relaxant succinylcholine or to help determine the cause of prolonged apnea after surgical anesthesia

When to Get Tested?

  • When you have symptoms of pesticide poisoning or on a regular basis when you are at risk of exposure to organophosphates, such as through work in the agriculture industry and/or frequent use of organophosphate insecticides
  • When you or a close relative have experienced prolonged apnea and muscle paralysis after use of the drug succinylcholine for a surgical operation

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Cholinesterases are enzymes that are involved in helping the nervous system to function properly.There are two separate cholinesterase enzymes in the body: (1) acetylcholinesterase, found in red blood cells as well as in the lungs, spleen, nerve endings, and the gray matter of the brain, and (2) pseudocholinesterase (butyrylcholinesterase), found in the serum as well as the liver, muscle, pancreas, heart, and white matter of the brain. Cholinesterase tests measure the activity of these enzymes.

Acetylcholinesterase is involved in transmission of nerve impulses by breaking down acetylcholine, a chemical that helps to transmit signals across nerve endings. A decrease in the activity of the enzyme acetylcholinesterase results in excess acetylcholine at nerve endings. This can lead to overstimulation of nerves within body tissues and organs. Pseudochlinesterase is involved in processing and metabolizing drugs.

The two most common reasons for testing activity levels in the blood are:

  • Organophosphate pesticide exposure. Insecticides containing organophosphates can inhibit cholinesterase and pseudocholinesterase activity. Symptoms can be severe with acute exposure to these pesticides or can gradually appear with chronic exposure. Absorption can occur by inhalation, ingestion, or contact with the skin. Testing red blood cell acetylcholinesterase and serum pseudocholinesterase may be done to detect acute poisoning or to monitor those with occupational exposure to these chemicals, such a farm workers or those who work with industrial chemicals.
  • Inherited pseudocholinesterase deficiency. Some individuals have an inherited deficiency due to a genetic variant of the enzyme pseudocholinesterase. This enzyme is used by the body to inactivate (metabolize) succinylcholine, a muscle relaxant that is commonly used during surgery. People who have low levels or defective pseudocholinesterase may experience prolonged effects of the drug, with protracted muscle paralysis and apnea following anesthesia. In addition, those who are homozygous for genetic variants may be at greater risk of adverse effects than those who are heterozygous. Pseudocholinesterase testing can be performed prior to surgery on those with a family history of prolonged apnea after use of succinylcholine to determine if they are at risk of complications related to this drug.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test



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