Pseudocholinesterase, Total (PCHE1)

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Test Code: PCHOTSO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Cholinesterase (Pseudo), Total, Serum Cholinesterase (Pseudochol), Butyrylcholinesterase

Useful For

Monitoring exposure to organophosphorus insecticides

Monitoring patients with liver disease, particularly those undergoing liver transplantation

Identifying patients who are homozygous or heterozygous for an atypical gene and have low levels of pseudocholinesterase

This tests is not useful for the differential diagnosis of jaundice.

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Serum	Serum Separator Tube (SST)	Red Top Tube (RTT)	1 mL	0.25 mL

Collection Processing Instructions

1. Patient's age and sex are required.

2. For cases of prolonged apnea following surgery, wait 24 hours before obtaining specimen.
3. Serum gel tubes should be centrifuged within 2 hours of collection.
4. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.

Specimen Stability Information

Specimen Type	Temperature	Time
Serum	Refrigerated (preferred)	14 days
	Frozen	365 days
	Ambient	24 hours

Rejection Criteria

Hemolysis	Gross
Lipemia	Gross
Icterus	Gross

Interference

There are some homozygous and heterozygous individuals who are sensitive to succinylcholine although their total pseudocholinesterase (PCHE) values are normal. A dibucaine inhibition test is necessary to confirm the presence of the abnormal allele in these individuals.

Certain drugs and anesthetic agents may produce in-vitro inhibition of the PCHE activity. Therefore, it is recommended that blood specimens be drawn 24 to 48 hours post-operatively on those patients who have experienced prolonged apnea after surgery.

Chemotherapy may interfere with test results, depending on the impact it has on the liver. PCHE levels may be lower due to this and if so, testing should be repeated at a later date.

Method Change: Pseudocholinesterase values measured after 1-28-2020 are approximately 80% increased compared to historical values and should be interpreted in the context of the current reference interval.

In very rare cases of gammopathy, in particular type IgM (Waldenstrom macroglobulinemia), may cause unreliable results.

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Report Available	Methodology/Instrumentation
Mayo Clinic Laboratories	Monday through Friday	1-3 days	Colorimetric Assay

Reference Lab

Mayo Clinic Laboratories

Test Information

Serum cholinesterase, often called pseudocholinesterase (PCHE), is distinguished from acetylcholinesterase or "true cholinesterase," by both location and substrate.

Acetylcholinesterase is found in erythrocytes, in the lungs and spleen, in nerve endings, and in the gray matter of the brain. It is responsible for the hydrolysis of acetylcholine released at the nerve endings to mediate transmission of the neural impulse across the synapse.

PCHE, the serum enzyme, is also found in liver, pancreas, heart, and white matter. Its biological role is unknown.

The organophosphorus-containing insecticides are potent inhibitors of the true cholinesterase and also cause depression of PCHE. Low values of PCHE are also found in patients with liver disease. In general, patients with advanced cirrhosis and carcinoma with metastases will show a 50% to 70% decrease. Essentially normal values are seen in chronic hepatitis, mild cirrhosis, and obstructive jaundice.

PCHE metabolizes the muscle relaxants succinylcholine and mivacurium, and therefore, alterations in PCHE will influence the physiologic effect of these drugs.

In normal individuals (approximately 94% of the population) certain drugs and other agents, such as dibucaine and fluoride, will almost completely inhibit the PCHE activity.

A small number of individuals (<1% of the population) have been shown to have genetic variants of the enzyme, and cannot metabolize the muscle relaxants succinylcholine and mivacurium and experience prolonged apnea. These individuals generally have low levels of PCHE, which is not inhibited by dibucaine or fluoride. These individuals are either homozygotes or compound heterozygotes for an atypical gene controlling PCHE.

Simple heterozygotes have also been identified who show intermediate enzyme values and inhibition.

Reference Range Information

Performing Location	Reference Range
Mayo Clinic Laboratories	Males: 5320-12,920 U/L
	Females: 0-15 years: 5320-12,920 U/L 16-39 years: 4260-11,250 U/L 40-41 years: 5320-12,920 U/L > or =42 years: 5320-12,920 U/L Note: Females age 18-41 years who are pregnant or taking hormonal contraceptives, the reference interval is 3650-9120 U/L.

Interpretation

Patients with normal pseudocholinesterase (PCHE) activity show 70% to 90% inhibition by dibucaine, while patients homozygous for the abnormal allele show little or no inhibition (0%-20%) and usually low levels of enzyme.

Heterozygous patients have intermediate PCHE levels and response to inhibitors.

The atypical gene is inherited in an autosomal recessive pattern. In a positive patient, family members should be tested.

Decreasing or low levels may indicate exposure to organophosphorus insecticides, as long as liver disease and an abnormal allele have been ruled out.

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
82480		1

Synonyms/Keywords

Cholinesterase (Pseudo), Total, Serum Cholinesterase (Pseudochol), Butyrylcholinesterase

Ordering Applications

Ordering Application	Description
Cerner	Pseudocholinesterase Total (PCHE1)
COM	Pseudocholinesterase Total (PCHE1)

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