Test Details
Methodology
Cholinesterase by spectrophotometry (Ellman) with dibucaine inhibition
Result Turnaround Time
3 - 5 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Test Includes
Dibucaine percent inhibition only
Use
This test is used to assess the presence of homozygous or heterozygous “atypical” cholinesterase variant in patients who have low cholinesterase activity result and may be at risk of apnea when given succinylcholine muscle relaxant.
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 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 sample is tested under standard conditions (inhibition expressed as a percent). This approach to detection of 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) cholinesterase level was slightly below the normal range.1
Specimen Requirements
Specimen
Serum
Volume
0.5 mL
Minimum Volume
0.2 mL
Container
Red-top tube or gel-barrier tube
Collection Instructions
Separate serum from cells and place in transport tube. Mark transport tube appropriately “serum.”
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
Storage Instructions
Room temperature
Patient Preparation
Do not collect within 24 hours of administration of muscle relaxant.
Causes for Rejection
Serum not separated from cells; frozen whole blood received; hemolysis
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 |