Cholinesterase, Serum and RBC
(RBC) Erythrocyte cholinesterase is measured to diagnose organophosphate and carbamate toxicity and to detect atypical forms of the enzyme. Cholinesterase is irreversibly inhibited by organophosphate insecticides and reversibly inhibited by carbamate insecticides. Serum or plasma pseudocholinesterase is a better measure of acute toxicity, while erythrocyte levels are better for chronic exposure. (Serum level returns to normal prior to normalizing of red cell level.
(Serum) Evaluate preoperative patients for succinylcholine (suxamethonium) anesthetic sensitivity, genetic or secondary to insecticide exposure, in appropriate circumstances. To prevent or evaluate prolonged anesthetic effect, prolonged apnea, after surgery. Very small amounts (0.04−0.06 mg/kg) of succinylcholine are needed to obtain 90% of neuromuscular blockade in patients with low levels of plasma cholinesterase activity.
Monitor organophosphorous or carbamate insecticide poisoning, in which level is decreased; establish patient’s baseline value before exposure. Indications include such pesticide exposure, especially with miosis, blurred vision, muscle weakness, twitching, and fasciculation, bradycardia, nausea, diarrhea, vomiting, salivation, sweating, pulmonary edema, arrhythmias, and convulsions. The value of assessing risk status in persons exposed to organophosphate insecticides on the basis of plasma or serum cholinesterase levels alone has been called into question. Are normal levels indicative of no exposure or of a genetic variant with or without exposure? There are interpretive problems with low or high values.
Family studies may be done when an individual with a genetically abnormal type is documented by serum pseudocholinesterase deficiency and, ideally, confirmed by phenotyping.
Serum and whole blood
2 mL serum and 7 mL whole blood
0.1 mL serum and 1 mL whole blood
Red-top tube or gel-barrier tube and lavender-top (EDTA) tube
Separate serum from cells in red-top tube and place in transport tube. Do not separate EDTA tube.
Whole blood (RBC): Stable at room temperature or refrigerated for 14 days and unstable frozen. Serum: Stable at room temperature, refrigerated, or frozen for 14 days; freeze/thaw cycles: stable x3.
Serum and whole blood samples not sent; anticoagulants other than EDTA (RBC only); frozen whole blood received; hemolyzed serum or whole blood
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