Table 3. Case definition matrix for acute pesticide poisoning.

Category	Probable case (meets at least one criterion in each category)	Possible case (meets at least one criterion in each category)	Unlikely/unknown case (meets at least one criterion in anya category)
Exposure	• Observation of pesticide residue, odour or other contamination by a health-care provider or trained personnel • A plausible description of exposure based on report by patient, witness or written record of pesticides used • Biological monitoring demonstrating evidence of the pesticide in the body (e.g. blood, serum, urine, sweat levels of specific chemicals) or evidence of a physiologic response to pesticide exposure (e.g. depressed cholinesterase levels after organophosphate exposure, prolonged prothrombin time after coumarin exposure) • Environmental sampling confirming presence of the chemical in the soil, clothing, air or water • Clinical response to administration of a treatment or antidote for pesticide poisoning (e.g. atropine, vitamin K)	• Observation of pesticide residue, odour or other contamination by a health-care provider or trained personnel • A plausible description of exposure based on report by patient, witness or written record of pesticides used • Biological monitoring suggesting presence (but not excess) of the pesticide in the body (e.g. blood, serum, urine, sweat levels of specific chemicals) • Environmental sampling confirming presence of the chemical in the soil, clothing, air or water	• No evidence of exposure • Evidence of no exposure
Health effects	Documentation by a health-care provider or trained personnel of: • a characteristic toxidrome or health effect from the pesticide • a physical signb consistent with pesticide exposure and not easily explained by another condition • a laboratory test consistent with pesticide exposure and not easily explained by another condition • three or more symptomsb (not verifiable by objective means) compatible with pesticide exposure • autopsy evidence of pesticide poisoning	Documentation by a health-care provider or trained personnel of: • a health effect from the pesticide exposure even in the absence of a specific toxidrome • an exacerbation of a pre-existing illness (e.g. triggering asthma) • two or more subjective symptoms reported by the patient without objective evidence of physical findings or laboratory evidence	• No documented signs or symptoms:b • only one subjective symptomb (not verifiable by objective means) • insufficient information on health effects
Causality	• Temporal cause-effect relationship between exposure and health effect consistent with the known toxicology of the pesticide	• Temporal cause–effect relationship between exposure and health effect consistent with the known toxicology of the pesticide • Temporal cause–effect relationship between exposure and health effect(s) consistent with published case reports of the health effects of the pesticide • Temporal relationship between exposure and health effect(s) that have not yet been observed provided there is no other likely explanation for the effects and the effects do not contradict present knowledge of the toxicology of the pesticide	• Implausible temporal cause–effect relationship between exposure and health effects • Health effects are not consistent with known toxicology or case reports of the pesticide • Insufficient causality information

^a Note that the other classifications require meeting criteria in each category as opposed to any.
^b A distinction is to be made between signs and symptoms. A physical sign is an objective finding that can be described by a health-care provider or trained personnel (e.g. diaphoresis, tachycardia, vomiting). A symptom is a subjective complaint reported by a patient (e.g. nausea, headache, dizziness).