Dibucaine Number With Serum and RBC Cholinesterase

Test ID: 

702906

CPT code:

82638, 82480, 82482

Synonyms:

• Cholinesterase Inhibition by Dibucaine
• Pseudocholinesterase Inhibition

Clinical 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.

Test 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.

Specimen Type:

Serum and whole blood

Requested Volume: 

2 mL plasma and 5 mL whole blood

Minimum Volume: 

0.1 mL plasma and 1 mL whole blood

Container Type: 

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

Patient Preparation: 

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

Collection:

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.

Rejection Criteria:

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