Normal cholinesterase level in the blood

Cholinesterase is a family of enzymes produced in the liver with an important role in the nervous system.

Cholinesterase is responsible for the rapid hydrolysis of acetylcholine released at nerve endings, which mediates the transmission of nerve impulses across the synapse.

There are two types of cholinesterase:

• Acetylcholinesterase (also called erythrocyte cholinesterase or AChE): It is anchored to the external surface of red blood cells (RBCs) and is also present in tissues such as the lungs, spleen, nerve endings, and gray matter of the brain.
• Pseudocholinesterase (also known as plasma cholinesterase, butyrylcholinesterase, or BuChE): It is primarily produced in the liver, but is also found in the pancreas, heart, serum, and white matter of the brain.

Acetylcholinesterase is responsible for the rapid hydrolysis of acetylcholine, released at nerve endings, to mediate the transmission of neural impulses across synapses.

Patients with low levels or reduced activity of pseudocholinesterase may experience a prolonged episode of apnea when administered suxamethonium, a muscle relaxant used during surgery. In these cases, it is possible to identify patients by quantifying serum cholinesterase activity.

A cholinesterase blood test has three main purposes:

• As a test of liver function: In the absence of genetic causes, a decrease in cholinesterase activity can reflect a liver disorder such as cirrhosis or hepatitis. It is also useful for monitoring liver function after liver transplantation.
• Perioperative management prior to anesthesia: Succinylcholine (suxamethonium) and mivacurium are muscle relaxants used in surgery. In patients with an uncommon genetic cholinesterase-deficiency disorder, these drugs may not be broken down quickly enough, leading to prolonged paralysis of the respiratory muscles (apnea).
• As an indicator of possible insecticide poisoning: Inhalation, ingestion, or contact with carbamate and organophosphorus pesticides (e.g., parathion, sarin, tetraethyl pyrophosphate) used in agriculture and organic chemical industries can inhibit cholinesterase activity. The degree of cholinesterase inhibition is proportional to the level of exposure.

A high level of cholinesterase in the blood may be associated with diseases such as diabetes, hyperlipidemia, high cholesterol, hypertension, and more. If levels are extremely high, it may indicate nephrotic syndrome.

Each laboratory must establish its own normal ranges for cholinesterase in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels, according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

The normal ranges of cholinesterase in the blood can vary significantly between laboratories, depending on factors such as the type of cholinesterase measured (acetylcholinesterase, pseudocholinesterase, or the sum of both), the sample used (blood, plasma, serum, or RBC), the measurement technique, and the substrate. For this reason, it is very important to refer to the specific normal range provided in your test report.

Cholinesterase levels in women are typically 10–15% lower than in men. In newborns, normal ranges are usually about half of adult levels. In children, cholinesterase levels gradually increase, reaching adult levels by around 6 years of age.

During pregnancy, cholinesterase values decrease by 20–30% in the first trimester, remain reduced throughout pregnancy, and return to normal levels a few weeks after childbirth.

The following values are considered to be normal values:

IMPORTANT: These levels are expressed in U/ml. They are an example of a healthy man of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.