Dibucaine Number

CPT: 82638
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Test Details


  • Dibucaine Inhibition

Test Includes

Dibucaine percent inhibition only


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

Reference Interval

Normal: 70% to 90% inhibition; heterozygotes: 30% to 70% inhibition; homozygotes: 0% to 30% inhibition

Additional Information

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

Specimen Requirements


Serum or plasma


0.5 mL

Minimum Volume

0.2 mL


Red-top tube, gel-barrier tube, or lavender-top (EDTA) tube

Patient Preparation

Do not collect within 24 hours of administration of muscle relaxant.


Separate serum or plasma from cells and place in transport tube. Mark transport tube appropriately “serum” or “plasma.”

Storage Instructions

Room temperature

Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Plasma or serum not separated from cells; frozen whole blood received; hemolysis

Clinical Information


1. Jackson SH, Bailey GW, Stevens G. Reduced plasma cholinesterase following haemodilutional cardiopulmonary bypass. Anaesthesia. 1982 Mar; 37(3):319-321. 7091605


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

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