Blood acetylcholinesterase and butyrylcholinesterase as biomarkers of cholinesterase depression among pesticide handlers

Abstract

Objective Agricultural pesticide handlers are at an elevated risk for overexposure to organophosphate (OP) pesticides, but symptoms can be difficult to recognize, making biomarkers invaluable for diagnosis. Occupational monitoring programs for cholinesterase depression generally rely on measuring activity of either of two common blood cholinesterases which serve as proxy measurements for nervous-system acetylcholinesterase activity: red blood cell acetylcholinesterase (AChE) and plasma butyrylcholinesterase (BChE). These biomarkers, however, may be affected differentially by some OPs and the relationship between them has not been well characterized. We aim to determine the association between blood acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity levels and assess whether they produce comparable classifications of clinical cholinesterase depression among organophosphate pesticide handlers. Methods Using blood samples from 215 participants of the Washington State Cholinesterase Monitoring Program, we quantified changes in AChE and BChE activity from before and after exposure to OP pesticides and calculated Pearson correlation statistics for correlation of AChE and BChE changes in activity, as well as weighted Kappa statistics for agreement of classification of clinical cholinesterase depression based on AChE versus BChE measurements. Results AChE and BChE activity measurements are weakly negatively correlated in our study population. Reaching a clinical threshold for diagnosis of cholinesterase depression based on the AChE marker did not correlate with reaching clinical depression based on the BChE marker. Conclusions Both AChE and BChE should be measured in monitoring programs because they may both give potentially important but disparate classifications of clinical cholinesterase depression.

Longitudinal Assessment of Blood Cholinesterase Activities Over 2 Consecutive Years Among Latino Nonfarmworkers and Pesticide-Exposed Farmworkers in North Carolina

“…Third, the use of 15% as the threshold for classifying cholinesterase activity reduction may have resulted in some false positives, though 15% is a generally accepted value. 38,39 Fourth, no data, including pesticide application records or biomarker assessment, were available to confirm pesticide exposure.…”

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“…Indeed, even in developed countries there exists the problem of low educational level in farmers. In a 2014 cohort study in the United States, among 215 farmers in a bio-surveillance program of the State of Washington, Strelitz finds that 63.72% of the 215 participants could not read in English (Strelitz et al, 2014). In this study, 93.83% of cotton farmers had more than 5 years of practice and 76.87% had 10 years.…”

Spatial learning impairment in prepubertal guinea pigs prenatally exposed to the organophosphorus pesticide chlorpyrifos: Toxicological implications

“…Since RBC AChE is very sensitive to inhibition by most OP compounds, RBC AChE inhibition is commonly used as a surrogate endpoint for health risk assessment of OP intoxication (Strelitz et al, 2014). …”