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Test Code LAB6446 T-Cell Receptor Gene Rearrangement, PCR, Blood

Additional Codes

 

Test Name in EPIC EPIC Test Code Mnemonic Mayo Test ID
T-CELL RECEPTOR GENE REARRANGEMENT LAB6446 TCGR TCGR

 

Reporting Name

T Cell Receptor Gene Rearrange, B

Useful For

Determining whether a T-cell population is polyclonal or monoclonal using blood specimens

Method Name

Polymerase Chain Reaction (PCR)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole blood


Shipping Instructions


Specimen must arrive within 7 days of collection.



Necessary Information


Include relevant clinical information and cytogenetic results, if available.



Specimen Required


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.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Ambient (preferred) 7 days
  Refrigerated  7 days

Reject Due To

Gross hemolysis Reject
Moderately to severely clotted Reject

Reference Values

An interpretive report will be provided.

Positive, negative, or indeterminate for a clonal T-cell population

Day(s) Performed

Monday through Friday

CPT Code Information

81340-TCB (T cell antigen receptor, beta) (eg, leukemia and lymphoma), gene rearrangement analysis to detect abnormal clonal population(s); using amplification methodology (eg, PCR)

81342-TCG (T cell receptor, gamma) (eg, leukemia and lymphoma), gene rearrangement analysis, evaluation to detect abnormal clonal population(s)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TCGR T Cell Receptor Gene Rearrange, B In Process

 

Result ID Test Result Name Result LOINC Value
18210 Final Diagnosis: 22637-3
608951 Signing Pathologist 19139-5

Test Classification

This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

Clinical Information

The T-cell receptor (TCR) genes (alpha, beta, delta, and gamma) are comprised of numerous, discontinuous coding segments that somatically rearrange to produce heterodimeric cell surface T-cell receptors, either alpha/beta (90%-95% of T cells) or gamma/delta (5%-10% of T cells). With rare exceptions (eg, some neoplastic B-lymphoid proliferations), other cell types retain the germline configuration of the TCR genes without rearrangement.

 

The marked diversity of somatic TCR-gene rearrangements is important for normal immune functions but also serves as a valuable marker to distinguish abnormal T-cell proliferations from reactive processes. A monoclonal expansion of a T-cell population will result in the predominance of a single TCR-gene rearrangement pattern. In contrast, reactive T-cell expansions are polyclonal (or multiclonal), with no single clonotypic population predominating in the population of T cells. These distributive differences in both TCR sequence and genomic rearrangement fragment sizes can be detected by molecular techniques (ie, polymerase chain reaction) and used to determine if a population of T cells shows monoclonal or polyclonal features.

Interpretation

An interpretive report will be provided.

 

Results will be characterized as positive, negative, or indeterminate for a clonal T-cell population.

 

In the appropriate clinicopathologic setting, a monoclonal result is associated with a neoplastic proliferation of T cells (see Cautions).

Cautions

To determine the significance of the result, it must always be interpreted in the context of other clinicopathologic information.

 

The interpretation of the presence or absence of a predominant T cell receptor (TCR)-gene rearrangement profile is sometimes subjective.

 

The detection of a clonal TCR-gene rearrangement by this test is not necessarily synonymous with the presence of a T-cell neoplasm. False-positive results can occur because of the sensitivity of polymerase chain reaction (PCR) technique and the problem of nonuniform (skewed) amplification of target T-cell gene rearrangements. The latter problem can occur when the total T-cell number in a sample is limited, or because of physiologic skewing of the T-cell repertoire as seen with aging, posttransplantation, or T-cell reactions in autoimmune or (nonlymphoid) malignancies. False-negative results can occur for many reasons, including tissue sampling, poor amplification, or failure to detect a small minority of T-cell gene segment rearrangements with the use of consensus PCR primers. In some cases, an indeterminate or equivocal result will occur because the pattern of gene rearrangements is abnormal (compared to typical polyclonal T-cell processes), but not definitive, for a monoclonal T-cell population. In these situations, distinction of a small monoclonal subpopulation from an over-represented, but reactive, population may not be possible.

Method Description

Genomic DNA is extracted from the blood. T-cell receptor beta (TCRB) and T-cell receptor gamma (TCRG) loci (official designations TRB and TRG, respectfully) are amplified by polymerase chain reaction (PCR) using a multiplex primer method based on the BIOMED-2 strategy. Specific primers are labeled with fluorochrome dyes, permitting precise fragment sizing of PCR products by capillary gel electrophoresis using a genetic analyzer. Each amplified locus is assessed for gene rearrangement patterns and an overall interpretation of the assay is made with regards to the presence or absence of a monoclonal population.(Unpublished Mayo method)

Report Available

5 to 10 days

Specimen Retention Time

Whole blood: 2 weeks; Extracted DNA: 3 months

Forms

1. Hematopathology Patient Information (T676)

2. If not ordering electronically, complete, print, and send a Hematopathology/Cytogenetics Test Request (T726) with the specimen.