Dibucaine Number
| Dibucaine Number | | | |
| Number | | 081513 |
| CPT | | 82638 |
| Synonyms | | Dibucaine Inhibition |
| Test Includes | | Dibucaine percent inhibition only |
| 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 |
| Collection | | Separate serum or plasma from cells and place in transport tube. Mark transport tube appropriately “serum” or “plasma”. |
| Storage Instructions | | Refrigerate at 2°C to 8°C. |
| Patient Preparation | | Do not collect within 24 hours of administration of muscle relaxant. |
| Causes for Rejection | | Plasma or serum not separated from cells; frozen whole blood received; hemolysis |
| Reference Interval | | Normal: 70% to 90% inhibition; heterozygotes: 30% to 70% inhibition; homozygotes: 0% to 30% inhibition |
| 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 |
| Limitations | | No single simple test currently exists that can detect all enzyme variants. |
| Methodology | | 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 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 |
| Footnotes | | - Jackson SH, Bailey GW, and Stevens G, “Reduced Plasma Cholinesterase Following Haemodilutional Cardiopulmonary Bypass,” Anaesthesia, 1982, 37(3):319-21
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