Field measurement of plasma and erythrocyte cholinesterases.

We have optimized Ellman-type plasma and erythrocyte cholinesterase assays for the field determination of pesticide exposure. The assays employ stable, premixed, inexpensive colorimetric reagents and a simplified kinetic measurement procedure using a novel battery-operable light-emitting-diode-source colorimeter (LEDSC). These methods were compared to a field tintometric method for cholinesterase currently in widespread use, using samples from organophosphate-intoxicated hospitalized patients. In comparison to the colorimetric method, the tintometric method was less precise and consistently underestimated the extent of pesticide exposure. Methods for the effective field determination of pesticide exposure using cholinesterase assays are critically evaluated with regard to their practical, biochemical, and medical relevance.