Test Details
Methodology
Cholinesterase by spectrophotometry (Ellman) with dibucaine inhibition
Result Turnaround Time
3 - 5 days
Use
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
Specimen Requirements
Test Includes
Dibucaine percent inhibition only
Limitations
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.
Custom 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
Serum or plasma
Volume
0.5 mL
Minimum Volume
0.2 mL
Container
Red-top tube, gel-barrier tube, or lavender-top (EDTA) tube
Storage Instructions
Room temperature
Causes for Rejection
Plasma or serum not separated from cells; frozen whole blood received; hemolysis
Collection Instructions
Separate serum or plasma from cells and place in transport tube. Mark transport tube appropriately “serum” or “plasma.”
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 14 days |
Refrigerated | 14 days |
Frozen | 14 days |
Freeze/thaw cycles | Stable x3 |
Reference Range
Normal: 70% to 90% inhibition; heterozygotes: 30% to 70% inhibition; homozygotes: 0% to 30% inhibition
Footnotes
LOINC® Map
| 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 |
| Order Code | 081513 | |||||
| Order Code Name | Dibucaine Number | |||||
| Order Loinc | 39354-6 | |||||
| Result Code | 081513 | |||||
| Result Code Name | Dibucaine Number | |||||
| UofM | % inhibition | |||||
| Result LOINC | 39354-6 |