Novel test and its automation for the determination of erythrocyte acetylcholinesterase and its application to organophosphate exposure.
BACKGROUND
Because of the lack of a 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 colourless 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 were evaluated. Acetylcholinesterase values were in the range of 0-14 UgHb(-1) in cases of organophosphate poisoning, in contrast with normal controls, who had AChE values of 24.4--37.9 UgHb(-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.


CONCLUSIONS
The method we propose for measurement of AChE was found to be simple, reliable and easily automatable in the routine clinical laboratory.
Bissbort
S H
SH
Department of Chemical Pathology, Faculty of Medicine, University of Pretoria, P.O. Box 2034, Pretoria 0001, South Africa. bissbort@mweb.co.za
Vermaak
W J
WJ
Elias
J
J
Bester
M J
MJ
Dhatt
G S
GS
Pum
J K
JK
D015086:2,6-Dichloroindophenol / Q000378:metabolism; D000110:Acetylcholinesterase / Q000097:blood*; D001331:Automation; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D062025:Organophosphate Poisoning; D009943:Organophosphorus Compounds / Q000097:blood; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D009943:Organophosphorus Compounds; D015086:2,6-Dichloroindophenol; D000110:Acetylcholinesterase