COMT

Test Code
COMT

CPT Code
81479

Specimen
Whole blood or buccal swabs

Volume
5 mL of whole blood or four buccal swabs 

Minimum Volume
3 mL of whole blood or four buccal swabs 

Container
Lavender-stopper (EDTA) tube or paper envelope for dried buccal swabs 

Storage Instructions
Maintain at room temperature or refrigerate

Cause for Rejection
Hemolyzed specimen; quantity not sufficient

General Purpose and Use
COMT is an enzyme that degrades dopamine and norepinephrine, primarily in the prefrontal cortex of the brain. A common single nucleotide polymorphism (SNP) 472G>A, also referred to by the amino acid change 158 Val>Met, is associated with altered COMT enzymatic activity.  The 158 Met allele has lower enzymatic activity resulting in less dopamine degradation and higher dopamine concentrations as compared to those carrying the Val allele. Conversely, the 158 Val allele has higher activity and results in lower dopamine levels in the prefrontal cortex.  Low dopamine concentrations are associated with cognitive impairments including working memory deficits.  Val/Val homozygotes with depression are less likely to achieve remission when treated with SSRI antidepressants, and Val/Val homozygotes with schizophrenia are less likely to demonstrate improved cognitive effects when treated with antipsychotics.  In contrast, the Met/Met homozygotes are more likely to achieve remission and demonstrate cognitive improvement when treated with SSRIs and antipsychotics, respectively.  The frequency of the 158 Met variant varies from 25-43% depending on the population studied.

Alleles detected
472G>A (158 VAL>MET)

Limitations
Other variants of the COMT gene that are not detected in this assay may influence drug response. All factors should be considered as part of the overall patient management strategy.

Methodology
Real-time polymerase chain reaction with fluorescence detection.

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