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.
