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Test Code
SynonymsCholinesterase Inhibition by Dibucaine; Pseudocholinesterase Inhibition
Container TypeGel barrier tube and lavender top tube (EDTA)
Supply Item Numberpicture1467 and picture1222
Specimen TypeSerum and whole blood
Preferred Volume2 mL serum and 5 mL whole blood
Emergency Minimum Volume0.1 mL serum and 1 mL whole blood
Patient PrepDo not collect within 24 hours of administration of muscle relaxant.
Specimen ProcessingSeparate serum from cells and transfer to a standard PAML aliquot tube marked "Serum". Do not separate EDTA tube.
Store and TransportAmbient (room temperature)
StabilityRoom Temp 2 weeks  Refrigerated 2 weeks  Frozen (-20 °C) Serum 2 weeks; Whole blood - Unacceptable  
Unacceptable ConditionSerum not separated from cells; serum and whole blood specimens not sent; anticoagulants other than EDTA (RBC only); frozen whole blood received; hemolyzed serum
CPT Codes82480, 82482, 82638
Interface Order Code84999.Z867
Billing CodeDIBCHL
MethodCholinesterase by Spectrophotometry (Ellman) with Dibucaine Inhibition
Reference Ranges
Dibucaine NumberInhibition70-90%
Cholinesterase, S1801-3537U/L
Cholinesterase, RBC5300-10000U/L
Compliance RemarksThis test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.
NotesUse: 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. 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.

No single simple test currently exists that can detect all enzyme variants.

Interface Codes
typeorder codetest descriptionresult coderesult descriptionunitsdecimal placesloinc code
r84999.Z867Dibucaine, S/RBC Cholines.82638.Z2Dibucaine Number% 39354-6
r84999.Z867Dibucaine, S/RBC Cholines.82999.Z34Cholinesterase, SU/L02098-2
r84999.Z867Dibucaine, S/RBC Cholines.82999.Z35Cholinesterase, RBCU/L02099-0