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  1. It is done on the serum of patients.
  2. Enzyme activity in the serum is stable for several weeks.
    1. Another reference says
      1. stable for 6 hours at room temperature.
      2. One week at 4 °C.
      3. 6 months at -70 °C
  3. The serum is stable at room temperature and also on refrigeration.


  1. Avoid hemolysis.
  2. Avoid repeated freezing and thawing.


  1. Advised when you are exposed to chemicals called organophosphates, which are used in pesticides. This test can help determine your risk of poisoning.
  2. This test is done to rule out poisoning (Organophosphorus).
  3. To diagnose liver disease.
  4. Before you receive anesthesia with succinylcholine, which may be given before certain procedures or treatments, including electroconvulsive therapy (ECT).
    1. Particularly in case of pseudocholinesterase deficiency before the anesthesia.
  5. Monitoring patients with liver disease, particularly those undergoing liver transplantation.
  6. Identifying patients who are homozygous or heterozygous for an atypical gene and have low levels of pseudocholinesterase.


  1. Serum cholinesterase is a test that looks at blood levels of enzymes like acetylcholinesterase and pseudocholinesterase.
  2. Cholinesterase is an enzyme of the hydrolase group. 
    1. It can catalyze the breakdown of an acyl group from various esters of choline and acetylcholine.
  3. Cholinesterase is of two types:
    1. Acetylcholinesterase.
    2. Pseudocholinesterase.
  4. Cholinesterase enzyme breaks down acetylcholine.
  5. Acetylcholinesterase is found in nerve tissue, red blood cells as well as in lung and spleen.
    1. It is present in the grey matter of the brain.
  6. Pseudocholinesterase is found primarily in the liver.
    1. It is also present in pancreas, heart, white matter of the brain and serum.
  7. These enzymes help the nervous system to work properly.
    1. Acetylcholinesterase and pseudocholinesterase, these are needed to send signals through nerves
  8. Acetylcholinesterase in RBCs is known as RBC cholinesterase.

  1. Pseudocholinesterase known as butyrylcholinesterase or plasma cholinesterase, help break down a chemical that nerves need to send signals.


  1. The difference between the two types of cholinesterase has to do with their respective preferences for substrates.
    1. Acetylcholinesterase hydrolyzes acetylcholine more quickly.
    2. Pseudocholinesterase hydrolyzes butyrylcholine more quickly.
    3. The half-life of pseudocholinesterase is approximately 8–16 hours.
    4. Pseudocholinesterase levels may be reduced in patients with advanced liver disease.
  2. The decrease must be greater than 75% before significant prolongation of neuromuscular blockade occurs with succinylcholine.

  1. Elevation of plasma pseudocholinesterase was observed in 90.5% of cases of acute myocardial infarction.
  2. The presence of Acetylcholinesterase can confirm several common types of birth defect, including abdominal wall defects and neural tube defects.

Normal Cholinesterase

Source 1

  1. Serum cholinesterase =  8 to 18 units/mL
    1. RBC cholinesterase = 5 to 10 units/mL (30 to 40 units/g of the hemoglobin).
  2. Typically, normal pseudocholinesterase values range between 8 and 18 units/mL.
    1. The values are low at birth and the first 6 months of life.
    2. Reference values have not been established for patients that are <18 years of age.

Source 2

The serum increased level is seen in:

  1. Nephrosis.
  2. Diabetes mellitus.
  3. Hyperlipidemia.

The serum decreased level is seen in:

  1. poisoning with organophosphate insecticide.
  2. Liver diseases like hepatitis.
  3. Cirrhosis with ascites or jaundice.
  4. Metastatic carcinoma.
  5. Obstructive jaundice.
  6. Congestive heart failure.
  7. Before you receive anesthesia with succinylcholine, which may be given before certain procedures or treatments, including electroconvulsive therapy (ECT).
  8. In the condition with low serum albumins like malnutrition, anemia, infections, Dermatomyositis, Acute MI, and liver diseases.

The Smaller decrease may be due to:

  1. Pregnancy.
  2. Use of birth control pills.

RBC increased level is seen in:

  1. Reticulocytosis.
  2. Sickle cell anemia.

RBC decreased level is seen in:

  1. Poisoning due to insecticide like organophosphorus.
  2. Congenital cholinesterase deficiency.

Possible References Used

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