Test ID: ACHS
Acetylcholinesterase, Erythrocytes
Useful For 
Suggests clinical disorders or settings where the test may be helpful
Detecting effects of remote (months) past exposure to cholinesterase inhibitors (organophosphate insecticide poisoning)
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 #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.
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.
31.2-61.3 U/g of hemoglobin
Interpretation Provides information to assist in interpretation of the test results
Activities less than normal are suspect for exposure to certain insecticides.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
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 Provides recommendations for further in-depth reading of a clinical nature
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
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