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- Dibucaine 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.
This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the Food and Drug Administration.
Cholinesterase by spectrophotometry (Ellman) with dibucaine inhibition
Normal: 70% to 90% inhibition; heterozygotes: 30% to 70% inhibition; homozygotes: 0% to 30% 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 detection 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
Serum or plasma
Separate serum or plasma from cells and place in transport tube. Mark transport tube appropriately “serum” or “plasma.”
Causes for Rejection
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|081513||Dibucaine Number||39354-6||081513||Dibucaine Number||% inhibition||39354-6|
|Reflex Table for Dibucaine Number|
|Order Code||Order Name||Result Code||Result Name||UofM||Result LOINC|