Dibucaine Number With Plasma and RBC Cholinesterase

CPT: 82480; 82482; 82638
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Test Details


  • Cholinesterase Inhibition by Dibucaine
  • Pseudocholinesterase Inhibition

Test Includes

Dibucaine number with RBC cholinesterase and plasma 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

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 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

Specimen Requirements


Plasma and whole blood


2 mL plasma and 5 mL whole blood

Minimum Volume

0.1 mL plasma and 1 mL whole blood


Lavender-top (EDTA) tube and transport tube marked “plasma”

Patient Preparation

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


Separate plasma from cells for one lavender-top tube only. Place in transport tube and mark “plasma.” Do not separate other EDTA tube.

Storage Instructions

Room temperature. Whole blood (RBC): Stable at room temperature or refrigerated for 14 days and unstable frozen. Plasma: Stable at room temperature, refrigerated, or frozen for 14 days; freeze/thaw cycles: stable x3.

Causes for Rejection

Plasma not separated from cells; plasma and whole blood samples not sent; anticoagulants other than EDTA (RBC only); frozen whole blood received; hemolyzed plasma or whole blood

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
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

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