Detecting effects of remote (months) past exposure to cholinesterase inhibitors (organophospate insecticide poisoning).
Acetylcholinesterase (AChE) is anchored to the external surface of the RBC. Activity is lower in patients with paroxysmal nocturnal haemoglobinuria (PNH) where the degree of acetylcholinesterase deficiency can be correlated with clinical severity.
Red cell AChE is most often used to detect past exposure to organophosphate insecticides with resultant irreversible 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 exposure for several months by measurement of the red cell enzyme. The effect of the specific insecticides may be important to know prior to testing.
Samples may be sent for monitoring workers occupationally exposed to organophosphorus compounds
RBC AchE: > 97 kU/L
Plasma ChE.: >160 daU/L
Whole EDTA blood
Health and Safety Laboratory