Novel test and its automation for the determination of erythrocyte acetylcholinesterase and its application to organophosphate exposure

Background: Because of the lack of 3 problem-free, reliable method for determination of erythrocyte acetylcholinesterase (AChE), we developed a simple kinetic method, which we found to be both reliable and suitable for automation in the routine clinical laboratory. Methods: Acetylthiocholine, used as substrate, is hydrolysed by acetylcholinesterase to yield acetate and thiocholine. Thiocholine reacts with dichlorophenolindophenol. a blue coloured compound, which is reduced to a colour less product, producing a linear decrease in absorption at 606 nm. If required, this assay can also be run at 600 nm with equally acceptable results. Results: The method was automated on the Synchron LX20 multianalyser (Beckman Instruments) and blood samples of 80 patients with clinically symptomatic organophosphate poisoning and 153 normal controls wore evaluated. Acetylcholinesterase values were in the range of 0-14 U gHb(-1) in cases of organophosphate poisoning, in contrast with normal controls, who had AChE values of 24.1-37.9 U gHb(-1). No overlap was found between AChE values of controls and poisoned cases. Intra- and inter-assay coefficients of variation were 1.68 and 3.71%, respectively. Conclusion: The method we propose for measurement of AChE was found to be simple, reliable and easily automatable in the routine clinical laboratory. (C) 2001 Elsevier Science B.V. All lights reserved.