CHOLINESTERASE, RBC/HGB RATIO

Code
000.0000
Name
CHOLINESTERASE, RBC/HGB RATIO
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
CPT Codes
82482
Site
SBMF
Reference Test
44078
ATLAS Test Code

Specimen Information

Type

Lavender, EDTA, WHOLE BLOOD

Volume

3.0 ml

Transport Info

Refrigerated

Fasting Required?
False
Patient Instructions

Reference Range

25-52 U/g Hgb

Methodology

Enzymatic

Clinical Significance

The measurement of cholinesterase levels may be particularly useful in suspected cases of organophosphate insecticide exposure/poisoning and in patients susceptible to prolonged apnea following surgical anesthesia.

The measurement of cholinesterase levels may be particularly helpful in suspected cases of organophosphate insecticide exposure/poisoning and in patients susceptible to prolonged apnea following surgical anesthesia. The latter is due to either low enzyme levels or atypical (activity) enzyme variants. The muscle relaxant succinylcholine is commonly used during anesthesia and will not be rapidly metabolized in these patients. True cholinesterase is found in RBCs and nervous tissues. Pseudocholinesterase is found in the plasma. True cholinesterase is responsible for inactivating the acetylcholine produced at the neuromuscular junction during neurotransmission. This is necessary to allow for subsequent repolarization of the nerve ending. True cholinesterase levels and activity are altered in organophosphate insecticide poisoning. In acute insecticide poisoning, the total cholinesterase (RBC and plasma) will be markedly reduced. Symptoms begin to appear at about 60% of normal activity and serious neuromuscular effects are seen at about 20% of normal. Total whole blood cholinesterase may be used as a screening test for acute and chronic exposure. Specific levels for RBC versus plasma cholinesterase differentiate exposure and recovery states. Levels are also decreased in liver disease (acute hepatitis, chronic hepatitis, cirrhosis, carcinoma), organophosphate poisoning, chronic renal disease, late stages of pregnancy, and estrogen therapy. Some patients have a genetic defect that will cause prolonged response and apnea when exposed to succinylcholine. The determination of human serum pseudocholinesterase (PChE) or cholinesterase (ChE) catalytic activity is frequently requested to detect patients with atypical enzyme variants. The atypical variants of cholinesterase are not able to hydrolyze succinylcholine. This defect can result in prolonged apnea. Low levels or even the absence of serum cholinesterase is indicative of atypical variants. By treating the patient's serum with dibucaine and measuring the residual PChE activity compared to the PChE of an untreated sample, the sensitivity to succinylcholine (a.k.a., anectine, suxamethonium, succinate) may be measured. However, patients with acute or chronic liver disease, organophosphate poisoning, chronic renal disease, late stages of pregnancy, and estrogen therapy may have markedly decreased PChE activities. Pseudocholinesterase phenotype interpretation is based on the total PChE activity and the percent of inhibition caused by dibucaine. While there are over 25 different phenotypes, most are extremely rare. Patients with unusual phenotypes cannot metabolize succinylcholine or mivacurium in the normal fashion and, therefore, these patients have prolonged apnea following the use of these drugs. Pseudocholinesterase, Dibucaine Inhibition (0020159) can identify the following phenotypes: U: Homozygote Usual (normal), frequency = 96%, indicates this patient will not have prolonged paralysis following the use of succinylcholine or mivacurium. UA: Heterozygote Usual/Atypical, frequency = 3%, indicates this patient will occasionally have prolonged paralysis following the use of succinylcholine or mivacurium. A: Homozygote Atypical, frequency 1 in 3000, indicates this patient will always have prolonged paralysis following the use of succinylcholine or mivacurium. US: Heterozygote Usual/Silent, frequency = 0.7%, indicates this patient will occasionally have prolonged paralysis following the use of succinylcholine or mivacurium. S: Homozygote Silent, frequency 1 in 40,000, indicates this patient will always have prolonged paralysis following the use of succinylcholine or mivacurium. AS: Heterozygote Atypical/Silent, frequency 1 in 80,000, indicates this patient will always have prolonged paralysis following the use of succinylcholine or mivacurium. F: Homozygote Fluoride Sensitive, frequency very rare, indicates this patient will have prolonged paralysis following the use of succinylcholine or mivacurium. The patient will be more susceptible with large dose and short surgery. FS: Heterozygote Fluoride Sensitive/Silent, frequency rare, indicates this patient will have prolonged paralysis following the use of succinylcholine or mivacurium. The patient will be more susceptible with large dose and short surgery. AF: Heterozygote, Atypical/Fluoride Sensitive, frequency rare, indicates this patient will have prolonged paralysis following the use of succinylcholine or mivacurium. The patient will be more susceptible with large dose and short surgery. UF: Heterozygotes Usual/Fluoride Sensitive, frequency rare, indicates this patient may rarely have prolonged paralysis following the use of succinylcholine or mivacurium. The patient will be more susceptible with large dose and short surgery.

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