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MLH1 Methylation
Test Code39782
CPT Codes
81288
Preferred Specimen
5 mL whole blood collected in an EDTA (lavender-top) tube, or ACD (yellow-top) tube, or
100 ng extracted DNA from a CLIA approved laboratory collected in TW or sterile water, or
Formalin-fixed paraffin-embedded tissue, or
1 H&E stained slide with 5 unstained slides (2 unstained minimum), non-baked slides with 5-10 um thick tumor sections
100 ng extracted DNA from a CLIA approved laboratory collected in TW or sterile water, or
Formalin-fixed paraffin-embedded tissue, or
1 H&E stained slide with 5 unstained slides (2 unstained minimum), non-baked slides with 5-10 um thick tumor sections
Minimum Volume
3 mL whole blood • 10 ng extracted DNA • 1 tissue block • 1 H&E slide
Instructions
H&E stained slides require Pathology report.
Transport Temperature
Room temperature
Specimen Stability
Whole Blood
Room temperature: 8 days
Refrigerated: 8 days
Frozen: Unacceptable
Extracted DNA
Room temperature: 5 years
Refrigerated: 5 years
Frozen: 10 years
Formalin fixed paraffin embedded tissue
Room temperature: 5 years
Refrigerated: 5 years
Frozen: Unacceptable
H&E Slide
Room temperature: 5 years
Refrigerated: Unacceptable
Frozen: Unacceptable
Room temperature: 8 days
Refrigerated: 8 days
Frozen: Unacceptable
Extracted DNA
Room temperature: 5 years
Refrigerated: 5 years
Frozen: 10 years
Formalin fixed paraffin embedded tissue
Room temperature: 5 years
Refrigerated: 5 years
Frozen: Unacceptable
H&E Slide
Room temperature: 5 years
Refrigerated: Unacceptable
Frozen: Unacceptable
Methodology
Real-Time Polymerase Chain Reaction
FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Setup Schedule
Wednesday Morning
Report available: 7 Days
Report available: 7 Days
Reference Range
Not detected
Clinical Significance
The MLH1 methylation assay is designed to target methylated CpG residues in the “C region of the MLH1 promoter. The target patients are the people with colorectal cancer who have positive MLH1 IHC or MSI high results. Promoter methylation of MLH1 can help to rule out Lynch syndrome in colorectal cancer patients, as well as women with endometrial cancer. Lynch syndrome is most frequently caused by inherited germline mutation of one or more of the DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2). The current NCCN guideline recommended testing for loss of protein expression of these MMR genes using immunohistochemistry (IHC) or microsatellite instability by PCR. MLH1 is the protein most often found to be downregulated or completely absent, often in combination with PMS2. This loss of expression of MLH1 can either be the result of a germline mutation(s) in the MLH1 gene (indicating Lynch syndrome), or due to promoter methylation (indicating a sporadic CRC). Few cases exist MLH1 germline methylation in Lynch syndrome. Usually there is 27.7-77.2% of concordance between BRAF mutation and MLH1 methylation confirming sporadic CRC.
