QJM Advance Access published online on March 28, 2008
QJM, doi:10.1093/qjmed/hcn026
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Predicting outcome using butyrylcholinesterase activity in organophosphorus pesticide self-poisoning
From the 1Scottish Poisons Information Bureau, Royal Infirmary of Edinburgh, and Clinical Pharmacology Unit, University of Edinburgh, UK, 2Department of Clinical Medicine, University of Colombo, Sri Lanka, 3South Asian Clinical Toxicology Research Collaboration, 4Walther Straub Institute of Pharmacology and Toxicology, Ludwig Maximilians University and 5Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany and 6Department of Clinical Pharmacology and Toxicology, Canberra Clinical School, ACT, Australia
Address correspondence to M. Eddleston, SPIB, Royal Infirmary, 51 Little France Crescent, Edinburgh EH16 4SA, UK. email: eddlestonm{at}yahoo.com
Received 27 December 2007 and in revised form 12 February 2008
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Abstract |
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Background: The usefulness of a low butyrylcholinesterase (BuChE) activity on admission for predicting severity in acute organophosphorus (OP) 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 BuChE activity, together with plasma OP concentration, for predicting death with two specific organophosphorus insecticides.
Design: A prospective cohort of self-poisoned 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 OP concentration were measured on admission and clinical outcomes recorded.
Results: The usefulness of a plasma BuChE activity <600 mU/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% (12.6–23.7). In contrast, while poorly sensitive for deaths in dimethoate poisoning [12/25 patients; 48%, (27.9–68.7)] it was reasonably specific [86.4% (75.7–93.6)]. A high OP concentration on admission was associated with worse outcome; however, a clear threshold concentration was only present for dimethoate poisoning.
Conclusions: Plasma BuChE activity on admission can provide useful information; however, it must be interpreted carefully. It can only be used to predict death when the insecticide ingested is known and its sensitivity and specificity for that insecticide has been studied. Plasma concentration of some OP insecticides predicts outcome. The development of rapid bedside tests for OP detection may aid early assessment of severity.