Rational use of cholinesterase activity testing in pesticide poisoning.

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.