Predicting outcome using Butyrylcholinesterase activity in organophosphorus pesticide self-poisoning

Abstract

The usefulness of a low butyrylcholinesterase activity on admission for predicting severity in acute organophosphorus insecticide poisoning has long been debated. Previous studies have been confounded by the inclusion of multiple insecticides with differing inhibitory kinetics. Aim-We aimed to assess the usefulness of admission butyrylcholinesterase activity, together with plasma organophosphorus concentration, for predicting death with identified organophosphorus insecticides. Design-A prospective cohort of selfpoisoned patients Methods-We prospectively studied 91 and 208 patients with proven dimethoate or chlorpyrifos self-poisoning treated using a standard protocol. Plasma butyrylcholinesterase activity and organophosphorus concentration were measured on admission and clinical outcomes recorded. Results-The usefulness of a plasma butyrylcholinesterase activity <600mU/ml on admission varied markedly - while highly sensitive in chlorpyrifos poisoning (sensitivity 11/11 deaths; 100%, 95%CI 71.5-100), its specificity was only 17.7% (95%CI 12.6-23.7). In contrast, while poorly sensitive for deaths in dimethoate poisoning (12/25 patients; 48%, 95%CI 27.9-68.7) it was reasonably specific (86.4%, 95%CI 75.7-93.6). A high organophosphorus concentration on admission was associated with worse outcome; however, a clear threshold concentration was only present for dimethoate poisoning. Conclusions-Plasma butyrylcholinesterase activity on admission can provide useful information; however, it must be interpreted carefully. It can only be used to predict need for critical care and death when the insecticide ingested is known and its sensitivity and specificity for that insecticide has been studied. Plasma concentration of some organophosphorus insecticides predicts outcome. The development of rapid bedside tests for organophosphorus detection may aid early assessment of severity.