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HelpTEST ID BCLL IGH Somatic Hypermutation Analysis, B-Cell Chronic Lymphocytic Leukemia (B-CLL), Varies
Reporting Name
IGH Somatic Hypermutation in B-CLLSpecimen Type
VariesShipping Instructions
1. Both refrigerated and ambient specimens must arrive within 7 days of collection.
2. Collect and package specimen as close to shipping time as possible.
Necessary Information
Specimen Required
Submit only 1 of the following specimens:
Specimen Type: Whole blood
Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Yellow top (ACD)
Specimen Volume: 4 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
3. Label specimen as whole blood.
Specimen Stability: Refrigerated (preferred) 7 days/Ambient 7 days
Additional Information: To ensure minimum volume and concentration of DNA are met, the requested volume must be submitted. Testing may be canceled if DNA requirements are inadequate.
Specimen Type: Bone marrow
Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Yellow top (ACD)
Specimen Volume: 2 mL
Collection Instructions:
1. Invert several times to mix bone marrow.
2. Send bone marrow specimen in original tube. Do not aliquot.
3. Label specimen as bone marrow.
Specimen Stability: Ambient (preferred) 7 days/Refrigerate 7 days
Additional Information: To ensure minimum volume and concentration of DNA are met, the requested volume must be submitted. Testing may be canceled if DNA requirements are inadequate.
Specimen Type: Extracted DNA from whole blood or bone marrow
Container/Tube: 1.5- to 2-mL screw-top tube
Specimen Volume: Entire specimen
Collection Instructions:
1. DNA must be extracted from blood or bone marrow within 7 days of collection.
2. Label specimen as extracted DNA and source of specimen
3. Provide volume and concentration of the DNA
Specimen Stability Information: Frozen (preferred)/Refrigerate/Ambient
Additional Information:
1. Specimens are preferred to be received within 1 year after DNA extraction.
2. DNA must be extracted in a CLIA-certified laboratory or equivalent and must be extracted from a specimen type listed as acceptable for this test (including applicable anticoagulants). We cannot guarantee that all extraction methods are compatible with this test. If testing fails, one repeat will be attempted, and if unsuccessful, the test will be reported as failed and a charge will be applied.
Specimen Minimum Volume
Whole blood/Bone marrow: 1 mL; Extracted DNA: 50 mcL at a concentration of 20 ng/mcL.
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Varies | |
Special Instructions
Method Name
Polymerase Chain Reaction (PCR) and Next-Generation Sequencing (NGS)
Reject Due To
| Gross hemolysis | Reject |
| Moderately to severely clotted | Reject |
Reference Values
An interpretive report will be provided.
Day(s) Performed
Monday through Friday
Report Available
14 daysSpecimen Retention Time
Whole blood/Bone marrow: 2 weeks; Extracted DNA: 3 monthsPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
81263-IGH (immunoglobulin heavy chain locus) (eg, leukemia and lymphoma, B-cell), variable region somatic mutation analysis
Forms
1. Molecular Hematopathology Patient Information (T711).
2. If not ordering electronically, complete, print, and send a Hematopathology/Cytogenetics Test Request (T726) with the specimen.
Useful For
Providing prognostic information in patients with newly diagnosed B-cell chronic lymphocytic leukemia
This test is not intended for use in providing prognostic information for patient with other B-cell neoplasms or hematopoietic tumors.
Clinical Information
During early B-cell development, IGH genes are assembled from multiple polymorphic gene segments that undergo rearrangements and selection, generating variable diversity joining (VDJ) combinations that are unique in both length and sequence for each B cell. In addition, newly acquired (somatic) point variations are introduced into the variable (V) regions of mature B cells during the germinal center reaction in lymph nodes in a process called somatic hypermutation (SHM). Since chronic lymphocytic leukemia (CLL) originates from the malignant transformation of single lymphoid cells, each daughter cell shares one or, sometimes, more unique "clonal" antigen receptor gene rearrangements, which are cell and tumor specific (ie, a tumor cell "fingerprint"). Clonal IGHV gene hypermutation status provides important prognostic information for patients with CLL and small lymphocytic lymphoma (SLL). The presence of IGH SHM is defined as greater than 2% difference from the germline VH gene sequence identity (mutated), whereas less than or equal to 2% difference is considered no SHM (unmutated). The status of SHM has clear influence on the median survival of CLL patients. Hypermutation of the IGH variable region is strongly predictive of a good prognosis, while lack of variants predicts a poorer prognosis.
Cautions
This test is useful for patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) with blood or bone marrow involvement. The prognostic value of somatic IGH V (IGHV) region mutation status is applicable only for this subtype of B-cell malignancy.
This test requires a minimum monoclonal CLL B-cell percentage in order to amplify the clonal IGH gene rearrangement. This level has been established at 5% of lymphocytes (eg, as determined by flow cytometric immunophenotyping). A CLL population below 5% will not have a reliable or reproducible clonal gene rearrangement and sequencing by next-generation sequencing to determine somatic mutation status will typically produce no results, or possibly a false-positive finding. Therefore, submitted CLL samples must have a minimum CLL monoclonal B-cell population of 5% of total lymphocytes.
The prognostic significance of somatic hypermutation status is only known when a single functional IGH rearrangement is identified (ie, in frame junctional coding region with no predicted premature protein truncation). However, a variety of situations can occur, for which the clinical significance is unknown at this time. These can broadly be grouped into the following:
1. Greater than 1 functional rearrangement is identified, with discordant mutation status
2. Only nonfunctional rearrangements are identified
Rearrangements with mutation status at or near the 2% cutoff should be interpreted with caution for the purposes of prognosis, particularly if the entire IGHV sequence could not be sequenced due to the use of framework region 1 V region primers. If such results are identified, an appropriate comment will be provided in the report.
Method Description
DNA is extracted from whole blood or bone marrow specimens, and IGH gene rearrangements are amplified by polymerase chain reaction using indexed leader and/or framework region 1 forward primers. The amplified product is then purified, and the DNA concentration measured. Pooled patient samples (identifiable by the index bar codes) are subjected to next-generation sequencing. FASTQC sequence data is subsequently analyzed using proprietary software to identify the IGH V rearrangement and the unique sequence. Results are compared to a germline IGHV sequence database by the software to calculate the percent identity of the tumor IGH V rearrangement to the closest germline sequence. Rearrangements containing a variation frequency of greater than 2% are interpreted as mutated. Rearrangements containing a variation frequency less than or equal to 2% are interpreted as unmutated.(Unpublished Mayo method)
Highlights
Although the determination of variant status can be accomplished by polymerase chain reaction followed by Sanger sequencing, that approach only allows for analysis of single samples at a time. Next-generation sequencing technology represents a significant improvement over existing Sanger assays by allowing for batch sample analysis and simultaneous identification of clonal IGH rearrangement, the tumor-specific rearrangement sequence, and determination of somatic variant percent.
Test name Meditech and ECW: IgVH B CELL CLL varies Mayo