Organic Phosphorous Compound and Carbamate Toxicity Workup

Updated: Sep 14, 2021
  • Author: Daniel K Nishijima, MD, MAS; Chief Editor: David Vearrier, MD, MPH  more...
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Laboratory Studies

The most common tests to determine organophosphorous compound (OPC) and carbamate poisoning are measurements of serum cholinesterase and red blood cell acetylcholinesterase (RBC AChE) activity, which are used to estimate neuronal AChE activity. The RBC AChE test provides a better indicator of neuronal AChE activity than serum AChE, but may not be as readily available. [19] In many health care centers, neither of these tests are immediately available and therefore are of no assistance in the acute setting or in guiding therapy.

Moreover, normal levels of enzyme activity vary widely in populations and in individuals. [26] Butyryl-cholinesterase activity may vary after exposure to cocaine, succinylcholine, morphine, and codeine.

These tests are most useful for confirming the diagnosis. In the ideal case, the diagnosis is confirmed with a decrease in enzyme activity from baseline (50% for RBC cholinesterase activity); unfortunately, a baseline, preexposure enzyme level is not available for most patients.

A high blood neutrophil-to-lymphocyte ratio (NLR) at hospital admission has been reported to be an independent risk factor for mortality. [27]   


Imaging Studies

In patients with respiratory distress due to bronchorrhea, chest radiograph findings may range from haziness to pulmonary edema. Serial chest radiographs in conjunction with pulse oximetry and auscultation may be used to guide therapy.



An electrocardiogram (ECG) may be considered. Retrospective studies have shown that a prolonged QTc interval is the most common ECG abnormality. [28, 22] Elevation of the ST segment, sinus tachycardia, sinus bradycardia, and complete heart block (rare) may also occur. Sinus tachycardia occurs just as commonly as sinus bradycardia.