ARUP's Laboratory Test Directory
| 0051286: Methotrexate Sensitivity by MTHFR Genotyping |
| Test Mnemonic: MTX MTHFR | |
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Methodology: Polymerase Chain Reaction/Fluorescence Monitoring
Performed: Sun-Sat Reported: 2-7 days |
| Specimen Required: | |
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Collect: One 3 mL lavender (EDTA) or pink (K2EDTA). Also acceptable: yellow (ACD Solution A), lt. blue (sodium citrate), or green (sodium or lithium heparin).
Transport: 3 mL whole blood at 2-8°C. (Min: 1 mL) Pediatric Collection/Transport: 1 mL whole blood at 2-8°C. Stability: Ambient: 3 days; Refrigerated: 1 week; Frozen: Unacceptable |
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| Reference Interval: |
| By report |
| Interpretive Data: | |
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Background Information: The C677T and the A1298C mutations in the methylenetetrahydrofolate reductase (MTHFR) gene correlate with reduced enzyme activity; however, only individuals homozygous for the C677T mutation or compound heterozygous for the C677T/A1298C mutations have significantly elevated plasma homocysteine levels. Homozygosity for the C677T mutation is associated with methotrexate-related toxicity. Homozygosity for the A1298C mutation is associated with lower methotrexate dose requirements. Methodology: Patient DNA is assayed for the C677T and the A1298C mutations in the MTHFR gene by polymerase chain reaction (PCR) and fluorescence monitoring using hybridization probes. Limitations: Mutations in other genes or mutations other than C677T and A1298C in the MTHFR gene may affect toxicity and efficacy of methotrexate. Analytical Sensitivity/Specificity: 99.9% This test is performed pursuant to an agreement with Roche Molecular Systems, Inc. This test is performed pursuant to an agreement with Siemens Medical Solutions. Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com. Please refer to Statement C in the Compliance Statements section in the front of the Laboratory Test Directory. |
| Note: | |
| For homocysteine levels by MTHFR genotyping, refer to test Methylenetetrahydrofolate Reductase Mutation Detection (Thermolabile Form) (C677T & A1298C) (0055655). |
| CPT Code(s): | |
| 83890 Isolation; 83900 Molecular diagnostics; 83896 x4 Nucleic acid probe; 83912 Interpretation and report - Additional CPT code modifiers may be required for procedures performed to test for oncologic or inherited disorders. |