Abstract:
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.
