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Detecting effects of remote (months) past exposure to cholinesterase inhibitors (organophosphate insecticide poisoning)
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.
31.2-61.3 U/g of hemoglobin
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.
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