Chlorinesterase Test

Other names: Butyrylcholinesterase; EC 3.1.1.8; Pseudo Cholinesterase; BChE; Acylcholine Acylhydrolase

There are two types of chlorinesterase enzyme in the body; this test is used to measure the butyrylcholinesterase (also known as pseudo cholinesterase) enzyme. Butyrylcholinesterase is found in the blood plasma, white matter and the intestine; it is used to metabolise the muscle relaxant suxamethonium. Butyrylcholinesterase is also altered by contact with organic phosphorus insecticides.

Why is the test used?

The test has two main uses; the first is to test for post-operative paralysis after a muscle relaxant known as suxamethonium has been used. The test is also used to test for organic phosphorus insecticides and compounds; some patients who work in the farming or chemicals industries may be exposed to these substances.

The test is usually ordered if a patient has family history of paralysis following the use of suxamethonium. The test is also carried out as a routine screening test for people who work with substances including Sarin, Parathion and tetraethyl pyrophosphate on a regular basis. The test can also test for acute exposure and may be ordered if the patient has symptoms such as vomiting, paralysis and in extreme cases, a coma.

How is the test performed?

The test is done by collecting and analysing a sample of blood. A needle is inserted into a vein in the arm (usually on the inside of the elbow) and the blood is collected in a syringe. Once the sample has been collected, it will be bottled, labelled with the patient’s name and sent away to the laboratory for analysis.

What do the test results mean?

Some people are more sensitive to suxamethonium than others; the level of sensitivity depends on the person’s phenotype. A UU phenotype is normal and will not carry any risks of paralysis, while a UA or UF phenotype may carry a small risk; people with AA or AS phenotypes may experience paralysis for 2 hours, while those with an SS phenotype may experience paralysis for up to three hours. People with FF, AF and FS phenotypes may experience intermediate effects when given suxamethonium.

A fall of cholinesterase activity may be caused by exposure to organic phosphorus compounds; serum cholinesterase usually falls by about 40% before symptoms appear and 80% once symptoms become more serious.

Other health conditions may also cause a fall in cholinesterase activity; these include renal disease, malnutrition, shock and some forms of cancer; pregnancy can also affect activity. Advanced or serious acute liver conditions can also affect cholinesterase activity.

Specific Blood Tests

Blood Test Guide

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