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Dibucaine Number With Serum and RBC Cholinesterase
- Cholinesterase Inhibition by Dibucaine
- Pseudocholinesterase Inhibition
Dibucaine number with serum and RBC cholinesterase
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 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 and whole blood
2 mL serum and 5 mL whole blood
0.1 mL serum and 1 mL whole blood
Separate serum from cells in red-top tube and place in transport tube marked “serum.” Do not separate EDTA tube.
Room temperature. 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.
Causes for Rejection
Serum not separated from cells; serum and whole blood specimens not sent; anticoagulants other than EDTA (RBC only); frozen whole blood received; hemolyzed serum
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|121152||Dibucaine, S/RBC Cholines.||081513||Dibucaine Number||% inhibition||39354-6|
|121152||Dibucaine, S/RBC Cholines.||121153||Cholinesterase, S||U/L||2098-2|
|121152||Dibucaine, S/RBC Cholines.||081539||Cholinesterase,RBC||U/L||2099-0|