A comparison of three methods for cholinesterase analysis

Three methods of cholinesterase analysis in blood are compared: the ΔpH (modified Michel method), pH Stat, and radiometric methods. The ΔpH method was determined to be the best choice for routine laboratory screeening for organophosphate exposure. The methods all agree within experimental variation. The radiometric method uses a thin-layer chromatography (TLC) separation of acetate (¹⁴C) activity from acetylcholine (¹⁴C) activity with direct β counting or scintillation counting to determine the concentration of acetate activity. The methods were compared on freeze-dried human blood and on experimentally carbamate-inhibited mouse blood. The radiometric analysis may be performed using as little as 5 μl of blood. The radiometric method may enhance the ability to detect sublethal exposure to cholinesterase inhibitors. It should be of particular use where sampling size is of greatest importance.