true cholinesterase

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an enzyme that splits acetylcholine into acetic acid and choline; it occurs primarily in the serum, liver, and pancreas. See also acetylcholinesterase.
true cholinesterase acetylcholinesterase.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


(a-sĕ'til-kō'lin-es'ter-ās), [MIM*100740]
The cholinesterase that hydrolyzes acetylcholine to acetate and choline within the central nervous system and at peripheral neuroeffector junctions (for example, motor endplates and autonomic ganglia).
Farlex Partner Medical Dictionary © Farlex 2012

true cholinesterase

Cholinesterase, see there.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

Red Blood Cell Cholinesterase

Synonym/acronym: Acetylcholinesterase (AChE), erythrocyte cholinesterase, true cholinesterase.

Common use

To assess for pesticide toxicity and screen for cholinesterase deficiency, which may contribute to unrecoverable apnea after surgical induction with succinylcholine.


Whole blood (1 mL) collected in a lavender-top (EDTA) tube.

Normal findings

(Method: Spectrophotometry, kinetic)
TestConventional Units
RBC cholinesterase5,300–10,000 international units/L


There are two types of cholinesterase: acetylcholinesterase (AChE), or “true cholinesterase,” which is found in red blood cells (RBCs), lung, and brain (nerve) tissue; and pseudocholinesterase, which is mainly found in the plasma, liver, and heart. RBC AChE is highly specific for acetylcholine. RBC cholinesterase is used to assist in the diagnosis of chronic carbamate or organophosphate insecticide (e.g., parathion, malathion) toxicity. Organophosphate pesticides bind irreversibly with cholinesterase, inhibiting normal enzyme activity. Carbamate insecticides bind reversibly. Serum or plasma pseudocholinesterase is used more frequently to measure acute pesticide toxicity. Pseudocholinesterase is also the test used to indicate succinylcholine sensitivity (see monograph titled “Pseudocholinesterase and Dibucaine Number”).

Patients with inherited cholinesterase deficiency are at risk during anesthesia if succinylcholine is administered as an anesthetic. Succinylcholine, a short-acting muscle relaxant, is a reversible inhibitor of acetylcholinesterase and is hydrolyzed by cholinesterase. Succinylcholine-sensitive patients may be unable to metabolize the anesthetic quickly, resulting in prolonged or unrecoverable apnea. This test, along with the pseudocholinesterase test, is also used to identify individuals with atypical forms of the enzyme cholinesterase. The prevalence of succinylcholine sensitivity is 1 in 2,000–4,000 homozygote and 1 in 500 heterozygote patients. There are more than 15 identified phenotypes; A, AS, S1, S2, F, AF, and FS are associated with prolonged apnea following the use of succinylcholine. Widespread preoperative screening is not routinely performed.

This procedure is contraindicated for



  • Monitor cumulative exposure to organic phosphate insecticides
  • Verify suspected exposure to organic phosphate insecticides

Potential diagnosis

Increased in

  • Hemolytic anemias (e.g., sickle cell anemia, thalassemias, spherocytosis, and acquired hemolytic anemias) (increased in hemolytic anemias as AChE is released from the hemolyzed RBCs)

Decreased in

    Insecticide exposure (organic phosphate insecticides inhibit AChE activity) Late pregnancy (related to anemia of pregnancy) Paroxysmal nocturnal hemoglobinuria (related to lack of RBC production by bone marrow) Relapse of megaloblastic anemia (related to underproduction of normal RBCs containing AChE)

Critical findings


Interfering factors

  • Drugs and substances that may increase RBC cholinesterase levels include echothiophate, parathion, and antiepileptic drugs such as carbamazepine, phenobarbital, phenytoin, and valproic acid.
  • Improper anticoagulant; fluoride interferes with the measurement and causes a falsely decreased value.

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching:   Inform the patient this test can assist in identification of pesticide poisoning.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex. Particularly important to report is exposure to pesticides causing symptoms including blurred vision, muscle weakness, nausea, vomiting, headaches, pulmonary edema, salivation, sweating, or convulsions.
  • Obtain a history of exposure to occupational hazards and medication regimen.
  • Obtain a history of the patient’s hematopoietic system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues,  as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions, unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • The patient with decreased values should be observed for signs of fluid volume excess related to compromised regulatory mechanisms, decreased cardiac output related to decreased myocardial contractility or arrhythmias, and pain related to inflammation or ischemia.
  • Social and Cultural Considerations: Recognize anxiety related to test results, and be supportive of impaired activity related to weakness and fear of shortened life expectancy. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to genetic counseling services and screening tests for other family members. Educate the patient regarding the use of a medic-alert bracelet to notify health-care workers of increased risk from exposure to medications that may lower cholinesterase activity.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include biopsy bone marrow, CBC, CBC RBC indices, CBC RBC morphology, Ham’s test, pseudocholinesterase, sickle cell screen, and vitamin B12.
  • Refer to the Hematopoietic System table at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners