Cholinesterase activity testing

Plasma cholinesterase activity

Organophosphates and carbamates inhibit plasma cholinesterase (also known as pseudocholinesterase or butyrylcholinesterase). Decreased activity of this enzyme is a highly sensitive marker of exposure to organophosphates or carbamates, but does not correlate with severity of poisoning. Diagnosis of organophosphate or carbamate poisoning is unlikely if the plasma cholinesterase activity is normal. Consider testing if the diagnosis is in doubt.

Red blood cell cholinesterase activity

Organophosphates and carbamates also inhibit red blood cell cholinesterase activity and this more closely reflects the inhibition of acetylcholinesterase activity at neural synapses. This test has better correlation with the severity of organophosphate or carbamate poisoning than plasma cholinesterase activity.

Red blood cell cholinesterase activity¹ of less than 25% normal is associated with severe poisoning.