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Test Code ACHS Acetylcholinesterase, Erythrocytes

Reporting Name

Acetylcholinesterase, RBC

Useful For

Detecting effects of remote (months) past exposure to cholinesterase inhibitors (organophosphate insecticide poisoning)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole Blood EDTA

Shipping Instructions

Specimen must arrive within 72 hours of draw.

Necessary Information

Date of draw is required.

Specimen Required

Container/Tube: Lavender top (EDTA)

Specimen Volume: 4 mL

Specimen Minimum Volume

2.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole Blood EDTA Refrigerated

Reference Values

31.2-61.3 U/g of hemoglobin

Day(s) and Time(s) Performed

Tuesday, Friday; 10 a.m.

Test Classification

This test has been cleared or approved by the U.S. 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


LOINC Code Information

Test ID Test Order Name Order LOINC Value
ACHS Acetylcholinesterase, RBC 49230-6


Result ID Test Result Name Result LOINC Value
ACHSR Acetylcholinesterase, RBC 49230-6

Clinical Information

Acetylcholinesterase (AChE) is anchored to the external surface of the RBC. Its appearance in a lysate of red cells is diminished in paroxysmal nocturnal hemoglobinuria (PNH). The use of red cell AChE for PNH has not gained widespread acceptance, and flow cytometry testing is most often used for PNH (see PANH/81156 PI-Linked Antigen, Blood).


Red cell AChE is most often used to detect past exposure to organophosphate insecticides with resultant inhibition of the enzyme. Both the pseudocholinesterase activity in serum and red cell AChE are inhibited by these insecticides, but they are dramatically different vis-a-vis the temporal aspect of the exposure. The half-life of the pseudo-enzyme in serum is about 8 days, and the "true" cholinesterase (AChE) of red cells is over 3 months (determined by erythropoietic activity). Recent exposure up to several weeks is determined by assay of the pseudo-enzyme and months after exposure by measurement of the red cell enzyme. The effect of the specific insecticides may be important to know prior to testing.


Activities less than normal are suspect for exposure to certain insecticides.


Make sure the potential offending agent is, indeed, an acetylcholinesterase inhibitor.


Pseudocholinesterase acitivity in serum is the appropriate test for succinylcholine sensitivity to anesthesia.

Clinical Reference

1. Robinson DG, Trites DG, Banister EW: Physiological effects of work stress and pesticide exposure in tree planting by British Columbia silviculture workers. Ergonomics 1993;36:951-961

2. Fuortes LJ, Ayebo AD, Kross BC: Cholinesterase-inhibiting insecticide toxicity. Am Fam Phys 1993;47:1613-1620

Method Description

The substrate acetylthiocholine is split by acetylcholinesterase into thiocholine and acetate. The thiocholine then reacts with dithiobisnitro benzoic acid (Ellmans Reagent) to form the colored product thionitrobenzoic acid which is measured at 405 nm.(Ellman GL, Courtney KD, Andres V Jr, Featherstone RM: A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem Pharmacol 1961;7:88-95)

Analytic Time

4 days

Specimen Retention Time

7 days

Reject Due To


Mild reject; Gross reject


Mild OK; Gross OK






NY State Approved


Method Name

Spectrophotometric-Thiocholine Production