A farmer is brought to the emergency department with profuse salivation, lacrimation, miosis, bradycardia, and muscle fasciculations after accidental exposure to a pesticide. Which enzyme activity in red blood cells is most diagnostically relevant?
- A Acetylcholinesterase (true cholinesterase) ✓
- B Pseudocholinesterase (plasma cholinesterase)
- C Monoamine oxidase
- D Alkaline phosphatase
Correct answer: A. Acetylcholinesterase (true cholinesterase)
Explanation
Organophosphorus compounds irreversibly inhibit acetylcholinesterase (true cholinesterase), which is present in red blood cells and nerve terminals. RBC acetylcholinesterase activity correlates best with synaptic inhibition and is the preferred diagnostic test. Plasma pseudocholinesterase also falls but is less specific as it can drop in liver disease and malnutrition.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
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