Rational Use of Cholinesterase Activity Testing in Pesticide Poisoning

Abstract

Background: The use of acetylcholinesterase (AChE) activity testing in pesticide poisoning often falls on family physicians when evaluating a suspected poisoning or when monitoring the health of pesticide applicators.Methods: A review of the literature and consideration of three illustrative cases shows misunderstandings in the pathophysiology of the enzyme and in procedures for effective testing and monitoring of AChE levels.Results and Conclusions: The physiologic characteristics of acetylcholine neurotransmission are described and related to carbamate and organophosphate poisoning. Pre-exposure monitoring is described using the California plan. A 23 percent variance in AChE levels exists among normal patients. It is necessary, therefore, to establish baseline levels to overcome individual variance. The practice of measuring of AChE levels in acute poisoning is limited. In employees who have been monitored and for whom baseline AChE levels have been established, a diagnosis of poisoning can be made by comparing postexposure AChE levels with baseline levels. If there is no baseline level recorded, and if the offending chemical is in question, the clinician must base treatment on the clinical signs and symptoms. (J Am Board Fam Pract 1999;12:307-14.)

Differentiation between Acetylcholinesterase and the Organophosphate-inhibited Form Using Antibodies and the Correlation of Antibody Recognition with Reactivation Mechanism and Rate

“…The colorimetric assay is considered rapid and capable of high throughput analysis, however, several limitations to this method exist: (a) control levels of cholinesterase activity must be obtained prior to analysis of OP exposure, (b) cholinesterase activity and exposure level are not directly correlated, and most importantly (c) this assay does not identify the structure of the OP-AChE conjugates. As indicated, different OP structures can form distinct OP-AChE conjugates that can yield different toxic outcomes, and therefore the need to determine the structure of the OP-AChE conjugate is essential to understand the reactivation and/or aging profile for a given OP (3,(7)(8)(9).…”

An Evaluation of Blood Cholinesterase Testing Methods for Military Health

“…This document provided an extensive literature review that related ambient exposures to OPs with the depression of ChE activity and suggested that 70% inhibition of AChE activity in the RBCs is "significant." Over the years, many other documents have become available that provide guidance on the use of ChE testing for medical and public health purposes (Weese, 2005;California Environmental Protection Agency (Cal/EPA, 2002;Lessenger and Reese, 1999).…”

“…For clinical decision-making that involves acute poisoning, the value of ChE test data for the diagnosis, treatment, and management of patients often depends on whether or not the poison is known or suspected to be a ChE-inhibitor, and whether the patient has baseline or pre-exposure ChE test data available (Lessenger and Reese, 1999). On the other hand, ChE test data is quite valuable for medical surveillance and/or biological monitoring of known or suspected exposures to OPs or carbamates.…”

“…The variability of AChE activity between individuals based simply on genetics, sex, race, or age is estimated as high as 23% (Lessenger and Reese, 1999). This underscores the importance of having individual baseline values of ChE activity when assessing exposures to ChE-inhibitors, although some methods of developing postexposure baselines have been proposed (Lessenger and Reese, 1999).…”

Can Galantamine Act as an Antidote for Organophosphate Poisoning? A Review

“…The presence of alcohol, nicotine and caffeine can also induce alterations in the levels of cholinesterase. So, the establishment of a baseline value for cholinesterase enzymes in a particular region is very essential [20,21] . The quantitative estimation of the cholinesterase from the blood samples can be analyzed using colorimetry [22] .…”