Student Research: Stefani Penn

MS, , 2011
Faculty Advisor: Christopher D. Simpson

Integration of a Cholinesterase Test Kit into Diagnosis and Clinical Practice for Monitoring Farm Worker Exposure to Pesticides


Class I and II organophosphate and carbamate pesticides act as cholinesterase inhibitors. Handlers exposed to these pesticides for 30 or more hours in a 30-day period are given the opportunity to participate in the Washington State Cholinesterase Monitoring Program. Currently, the monitoring program requires three blood samples be shipped from the clinic to a central lab with 3-day turnaround for results. The Test-mate Cholinesterase (ChE) Test system (test kit) was used for cholinesterase activity testing in clinics. The test kit requires 10 microliters of blood and provides results in 4 minutes using the same Ellman methodology used by the laboratory. The kit was used to test a Frozen Baseline Model, where baseline samples are frozen at the clinic and tested in conjunction with the post-exposure samples upon the patients' return.

Application of the test kit was expanded to include verification of cholinesterase inhibition by detecting enzyme reactivation in blood using 2-pyridinealdoxime methocholoride (2-PAM). Laboratory studies were performed in vitro to determine optical reactivation conditions of pesticide-inhibited acetylcholinesterase and butyrylcholinesterase. These conditions were then utilized in experimental reactivation of farm worker blood using 2-PAM. Pesticide exposure blood incubated with one hundred microliters of 2-PAM for 30 minutes provides maximum potential reactivation of acetylecholinesterase; pesticide-exposed blood incubated with two hundred microliters of 2-PAM from 60 minutes provides maximum potential reactivation of butyrylcholinesterase.

Test kit verification of cholinesterase reactivation using 2-PAM may lead to further applications of the kit to clinical practice and may provide a method for specific diagnoses of cholinesterase inhibition. A use manual and informative material for the Frozen Baseline Model were developed and adapted to fit into a clinic's operating procedures. These materials could be used to integrate the test kit into clinics throughout Washington State and elsewhere, improving diagnosis of overexposure to organophosphate pesticides. The Frozen Baseline Model may prevent expensive laboratory analysis of farm workers' baseline samples if they do not return for post-exposure testing and will cut down on diagnostic time because testing will be done at the clinic.