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 dete rmination of erythrocyte acetylcholinesterase (AChE), we developed a simple kinetic method, which we found to be both reliable and suitable for automa tion in the routine clinical laboratory. Methods: Acetylthiocholine, used a s substrate, is hydrolysed by acetylcholinesterase to yield acetate and thi ocholine. Thiocholine reacts with dichlorophenolindophenol. a blue coloured compound, which is reduced to a colour less product, producing a linear de crease 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 o n the Synchron LX20 multianalyser (Beckman Instruments) and blood samples o f 80 patients with clinically symptomatic organophosphate poisoning and 153 normal controls wore evaluated. Acetylcholinesterase values were in the ra nge of 0-14 U gHb(-1) in cases of organophosphate poisoning, in contrast wi th 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 in ter-assay coefficients of variation were 1.68 and 3.71%, respectively. Conc lusion: The method we propose for measurement of AChE was found to be simpl e, reliable and easily automatable in the routine clinical laboratory. (C) 2001 Elsevier Science B.V. All lights reserved.