Test Catalog

Test Id : PCHE1

Pseudocholinesterase, Total, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

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.


Pseudocholinesterase (PCHE) testing has two main uses:

-Monitoring for toxic exposure in people who work with organophosphate compounds by establishing a baseline PCHE activity level. Then routine testing is used to monitor for a significant reduction in PCHE activity.

-Preoperative screening for patients with a history or family history of prolonged paralysis and apnea after the use of the muscle relaxant, succinylcholine, for anesthesia


This test can also diagnose acute organophosphate pesticide exposure.

Method Name
A short description of the method used to perform the test

Colorimetric Assay

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Pseudocholinesterase, Total, S

Lists additional common names for a test, as an aid in searching


Cholinesterase (Pseudo), Total

Serum Cholinesterase (Pseudochol)

Specimen Type
Describes the specimen type validated for testing


Necessary Information

Patient's age and sex are required.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: For cases of prolonged apnea following surgery, wait at least 24 hours before obtaining specimen.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.25 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

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

Useful For
Suggests clinical disorders or settings where the test may be helpful

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.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 the liver, the pancreas, the heart, and in the white matter of the brain. 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 therefore, 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 Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


5320-12,920 U/L


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.

Provides information to assist in interpretation of the test results

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.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Soliday FK, Conley YP, Henker R: Pseudocholinesterase deficiency: A comprehensive review of genetic, acquired, and drug influences. AANA J. 2010;78:313-320

2. Robles A, Michael M, McCallum R: Pseudocholinesterase deficiency: What the proceduralist needs to know. Am J Med Sci. 2019 Mar;357(3):263-267. doi: 10.1016/j.amjms.2018.11.002

3. Lurati AR: Organophosphate exposure with pseudocholinesterase deficiency. Workplace Health and Saf. 2013 Jun;61(6):243-245. doi: 10.1177/216507991306100602

4. den Blaauwen DH, Poppe WA, Tritschler W: Cholinesterase (EC with butyrylthiocholine-iodide as substrate: References depending on age and sex with special reference to hormonal effects and pregnancy. J Clin Chem Clin Biochem. 1983;21:381-386

Method Description
Describes how the test is performed and provides a method-specific reference

Cholinesterase catalyzes the hydrolysis of butyrylthiocholine to thiocholine and butyrate. Thiocholine instantaneously reduces the yellow hexacyanoferrate (III) to the almost colorless hexacyanoferrate (II). This decrease in color can be measured photometrically.(Package insert: Roche Cholinesterase Gen 2 Reagent, c501. Roche Diagnostics Corp; V 9.0, 01/2017)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 3 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

7 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
PCHE1 Pseudocholinesterase, Total, S 2098-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
PCHE1 Pseudocholinesterase, Total, S 2098-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports