PATTERN OF BLOOD PSEUDOCHOLINESTERASE AND ACETYLCHOLINESTERASE ACTIVITIES IN ACUTE CHLORPYRIFOS-POISONING

Introduction: The increased use of synthetic chemicals and drugs has made poisoning a worldwide problem with a significant rise in poisoning cases. Organophosphate (OP) pesticides are among the most widely used pesticides in the Asian countries including India. The measurement of serum or plasma pseudo cholinesterase (PChE) and RBC acetylcholinesterase (RBC-AChE) activities is used widely to investigate incidents of OP over-exposure, or as part of health surveillance in workers at risk of OP exposure. This study was planned to see the pattern of blood pseudocholinesterase, RBC-AChE activities and their ratios in chlorpyrifos-poisoning in relation to other OPs among the acute poisoning cases referred to the Poison Information Centre, National Institute of Occupational Health, Ahmedabad (PIC-NIOH).

Materials and Methods: OP-poisoning cases (n=705) referred to PIC- NIOH during Jan 2007-Dec 2011 (5 years) are included in this study. The data were analysed with respect to age, sex, route of exposure, mode, circumstances of exposure and type of OP encountered in poisoning. The blood samples were analysed for plasma cholinesterase and RBC-AChE activities on the day of admission to the hospital. The data of their activities and the ratio PChE/RBC-AChE in acute poisoning of chlorpyrifos, monocrotophos, dimethoate and phorate (more frequently encountered OPs; n=307) are reported.

Results: Chlorpyrifos, phorate, dimethoate and monocrotophos were commonly encountered OP-pesticides in poisoning; chlorpyriphos showing the highest frequency. In chlorpyrifos-poisoning, RBC-AChE activities were found to be significantly higher than dimethoate or monocrotophos poisoning. Higher RBC-AChE/PChE ratio was observed in chlorpyrifos-poisoning as compared to phorate-, dimethoate- or monocrotophos-poisoning group.

Conclusions: Variation in pattern of plasma pseudocholinesterase, RBC-AChE activities and RBC-AChE /PChE ratio was observed among the cases of chlorpyrifos, phorate, dimethoate and monocrotophos poisoning. Typically, higher RBC-AChE/ PChE ratio was observed in chlorpyrifos-poisoning as compared to phorate-, dimethoate- or monocrotophos-poisoning group which may be used as a diagnostic tool for acute exposure to chlorpyrifos.