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What is Cholinesterase test? 

Cholinesterases are enzymes that help regulate the normal functioning of the nervous system. They break down a neurotransmitter called acetylcholine so that it does not cause over-stimulation of muscles. However, certain chemicals such as pesticides - if they find a way into our body - can interfere with the functioning of cholinesterase, leading to breathing difficulty and muscle weakness

A cholinesterase test is done to assess chemical toxicity in the blood caused by such chemicals by measuring the activity of the cholinesterase enzyme. 

  1. Why is a Cholinesterase test performed?
  2. How do you prepare for a Cholinesterase test?
  3. How is a Cholinesterase test performed?
  4. Cholinesterase test results and normal range

Doctors order this test to diagnose organophosphate pesticide exposure/poisoning. It is especially recommended to people who handle organophosphate compounds in chemical industries. Exposure to these compounds can damage nerve-muscle coordination by inhibiting the breakdown of acetylcholine. Intoxication due to these compounds could lead to severe damage of organs such as lungs, skin and our digestive system. These toxins could enter the body through inhalation, direct ingestion or absorption through the skin. 

The symptoms of toxicity could be as follows:

If the toxicity progresses, the symptoms could be:

  • Vomiting
  • Vision difficulties
  • Lack of muscular coordination
  • Slowed breathing
  • Seizures and coma

If such symptoms are present, the doctor will order this test.

Furthermore, a cholinesterase test may also be performed several days before a surgery to check if an individual with an inherited deficiency of pseudocholinesterase is at risk of postoperative paralysis. Pseudocholinesterase is a type of cholinesterase that neutralises the effects of the muscle relaxant succinylcholine given as an adjunct to anaesthesia before surgery. However, those with a family history of post-operative paralysis are at risk of developing complications related to this drug.

You do not require any special preparation for this test. 

In order to conduct the test, the doctor or laboratory technician will collect a blood sample from a vein in your arm using a sterile needle. Sometimes, more than one needle insertion may be required. 

The risks associated with taking a blood sample are minimum. Aside from the fact that there may be some pain while the blood is being drawn, some other risks are:

  • Difficulty in obtaining the sample
  • Excessive bleeding at the site from where the blood is drawn
  • Fainting 
  • Haematoma (accumulation of blood under the skin)
  • Infection at the site where the needle is inserted

However, these risks can easily be reduced if proper precautionary measures are taken.

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Normal results:

The normal pseudocholinesterase values range from 8 to 18 units per millilitre (U/mL).

The normal values may vary slightly depending upon the laboratory where you are getting tested. Speak to your doctor to know the meaning of your test results.

Abnormal results:

Abnormal results would mean a decrease in the pseudocholinesterase levels. This could be due to:

Reduced cholinesterase levels can also be attributed to pregnancy, certain types of cancers, shock and renal disease.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

References

  1. Wu A. Tietz Clinical Guide to Laboratory Tests. 4thed. Saunders Elsevier, St Louis, MO. Pp: 250-251.
  2. Pagana K, Pagana T. link]. 4th ed. Pp: 171-172.
  3. Aminoff MJ, So YT. Effects of toxins and physical agents on the nervous system. In: Daroff RB, Jankovic J, Mazziotta JC, Pomeroy SL, eds. Bradley’s Neurology in Clinical Practice. 7th ed. Philadelphia, PA: Elsevier; 2016: chap 86.
  4. Nelson LS, Ford MD. Acute poisoning. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016: chap 110.
  5. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Cholinesterase - blood

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