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Dibucaine Number With Plasma and RBC Cholinesterase
- Cholinesterase Inhibition by Dibucaine
- Pseudocholinesterase Inhibition
Assess the presence of homozygous or heterozygous “atypical” cholinesterase variant, in patients who have low result of serum or plasma cholinesterase assay, and may be at risk of apnea when given succinylcholine muscle relaxant.
No single simple test currently exists that can detect all enzyme variants.
Cholinesterase by spectrophotometry (Ellman) with dibucaine inhibition
The degree of serum or plasma cholinesterase inhibition produced by dibucaine is under genetic control. Sensitivity to succinyl choline is dependent upon at least four allelic genes. The total quantitative cholinesterase determination may not be reliable in detecting sensitivity to succinyl choline as variant enzymes exhibit qualitative and quantitative differences in substrate specificity.
The dibucaine number indicates the percent inhibition of enzyme activity by this agent when a serum or plasma sample is tested under standard conditions (inhibition expressed as a percent). This approach to detecting the presence of serum or plasma cholinesterase variants does not entirely avoid the problem of variation in reactivity with some atypical enzymes. Prolonged apnea following hemodilutional cardiopulmonary bypass has been reported in a patient whose admission (preoperative) plasma cholinesterase level was slightly below the normal range.1
Plasma and whole blood
2 mL plasma and 5 mL whole blood
0.1 mL plasma and 1 mL whole blood
Separate plasma from cells for one lavender-top tube only. Place in transport tube and mark “plasma.” Do not separate other EDTA tube.
Causes for Rejection
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|081455||Dibucaine, Pl+RBC Cholines.||081513||Dibucaine Number||% inhibition||39354-6|
|081455||Dibucaine, Pl+RBC Cholines.||081521||Cholinesterase, Plasma||U/L||2098-2|
|081455||Dibucaine, Pl+RBC Cholines.||081539||Cholinesterase,RBC||U/L||2099-0|
|Reflex Table for Dibucaine Number|
|Order Code||Order Name||Result Code||Result Name||UofM||Result LOINC|