Clinical confirmation of organophosphate poisoning by serial cholinesterase analyses.

Three groups of agricultural workers with a history of exposure to organophosphate pesticides were followed up to evaluate the utility of sequential postexposure cholinesterase analyses to confirm organophosphate intoxication in the absence of baseline cholinesterase values. Three or more cholinergic symptoms were reported by 50 of the 72 patients. Initial plasma and red blood cell cholinesterase values of 45 of the workers were above the lower limit of the laboratory normal range. Follow-up examinations, including cholinesterase analyses, were conducted on 57 patients. When final postexposure cholinesterase determinations were taken as estimates of individual normal baseline values, the plasma and red blood cell activity of the three groups was shown to have been inhibited. The data support the use of sequential postexposure plasma cholinesterase analyses to confirm the diagnosis of organophosphate-induced illness in the absence of baseline values.