Case Definition: Nerve Agents or Organophosphates
Nerve agent or organophosphate toxicity might result from multiple routes of exposure. It consists of a cholinergic syndrome of excess respiratory and oral secretions, diarrhea and vomiting, diaphoresis, convulsions, altered mental status, miosis, bradycardia, and generalized weakness that can progress to paralysis, respiratory arrest and death (1-3).
In certain cases, excessive autonomic activity from stimulation of nicotinic receptors will predominate in the syndrome and will manifest as fasciculations, hypertension, mydriasis, and tachycardia.
Laboratory criteria for diagnosis
- Biologic: A case in which nerve agents in urine are detected, as determined by CDC or a LRN laboratory that has this capacity. Decreased plasma or red blood cell cholinesterase activity based on a specific commercial laboratory reference interval might indicate a nerve agent or organophosphate exposure; however, the reference intervals for cholinesterase activity are wide, which makes interpretation of these values difficult without a baseline measurement or repeat measurements over time.
- Environmental: Detection of organophosphate pesticides in environmental samples (6-10). However, a confirmation test for nerve agents in environmental samples is not readily available.
- Suspected: A case in which a potentially exposed person is being evaluated by health-care workers or public health officials for poisoning by a particular chemical agent, but no specific credible threat exists.
- Probable: A clinically compatible case in which a high index of suspicion (credible threat or patient history regarding location and time) exists for nerve agent or organophosphate pesticide exposure, or an epidemiologic link exists between this case and a laboratory-confirmed case.
- Confirmed: A clinically compatible case in which laboratory tests have confirmed exposure.
The case can be confirmed if laboratory testing was not performed because either a predominant amount of clinical and nonspecific laboratory evidence of a particular chemical was present or the etiology of the agent is known with 100% certainty.
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