What are other Names for this Test? (Equivalent Terms)
- T-Cell Antigen Receptor, Gamma Polypeptide, T-Cell Receptor, Gamma Cluster Mutation Analysis Test
- T-Cell Receptor Gamma Mutation Analysis Test
- TCRG Mutation Analysis Test
What is TRG Mutation Analysis Test? (Background Information)
- TRG mutation refers to an alteration in the T-cell receptor gamma (TRG) gene. It is associated with cancer of the white blood cells (leukemia) and immune deficiency
- The TRG gene gives instructions for the TRG protein. Like other T-cell receptors, TRG resides on the surfaces of specialized immune cells called T-cells
- T-cells are responsible for defending the body against pathogens present inside cells, such as viruses and bacteria, as well as cancerous cells and other offending agents
- T-cells recognize, and communicate with, other cells using their T-cell receptors. The T-cell receptor on a T-cell interacts with the major histocompatibility complex (MHC) of other cells
- The TRG protein is essential to the healthy functioning of the immune system. Problems with the TRG protein may impair communication of T-cells with other cells, compromising their immunoprotective abilities
- Most important clinically, TRG proteins are usually found in a fixed ratio relative to other T-cell receptors, and occur in pairs: 95% of T-cells possess a TRA/TRB combination, whereas only 5% possess the TRG/TRD combination
- Problems with the TRG gene may result in an abnormal TRG protein. Because of the key role TRG plays in the proper functioning of T-cells, this may contribute to, and indicate, leukemia, immune deficiency, and other immune system diseases
The molecular testing, in general, can be performed using a variety of methods. Some of these methods include:
- In situ hybridization techniques, such as fluorescence in situ hybridization (FISH)
- Immunohistochemistry (IHC)
- Next-generation sequencing (NGS)
- Polymerase chain reaction (PCR)
- Comparative genomic hybridization (CGH)
- Karyotyping including spectral karyotyping
- mRNA analysis
- Tissue microarrays (TMAs)
- Southern blot test
- Northern blot test
- Western blot test
- Eastern blot test
The methodology used for the test may vary from one laboratory to another.
Note: Molecular testing has limitations due to the molecular method and genetic mutational abnormalities being tested. This can affect the results on a case-by-case basis. Consultation with your healthcare provider will help in determining the right test and right molecular method, based on individual circumstances.
What are the Clinical Indications for performing the TRG Mutation Analysis Test?
Following are the clinical indications for performing the TRG Mutation Analysis Test:
- Fever or chills
- Persistent fatigue, weakness
- Frequent or severe infections
- Losing weight without trying
- Swollen lymph nodes, enlarged liver or spleen
- Easy bleeding or bruising
- Recurrent nosebleeds
- Tiny red spots in the skin (petechiae)
- Excessive sweating, especially at night
- Bone pain or tenderness
- Frequent and recurrent pneumonia, bronchitis, sinus infections, ear infections, meningitis or skin infections
- Inflammation and infection of internal organs
- Blood disorders, such as low platelet counts or anemia
- Digestive problems, such as cramping, loss of appetite, nausea and diarrhea
- Delayed growth and development
- Autoimmune disorders, such as lupus, rheumatoid arthritis, or type 1 diabetes
In general, the molecular genetic testing is undertaken in the following situations:
- To assist (and in some cases, confirm) the initial diagnosis
- If there is a family history of the medical disorder/condition
- To distinguish other conditions that have similar features (signs and symptoms)
- To help in determining treatment options
- To confirm recurrence of the tumor: Tumor recurrence can either be at the original tumor site, or at a distant location (away from the initial site)
How is the Specimen Collected for the TRG Mutation Analysis Test?
Following is the specimen collection process for TRG Mutation Analysis Test:
The specimen sample requirements may vary from lab to lab. Hence, it is important to contact the testing lab for exact specimen requirements, before initiating the testing process.
- Sample on which the test is performed may include:
- Peripheral blood in individuals showing signs and symptoms suspected of TTT
- In case of expectant mothers, prenatal testing through amniotic fluid and chorionic villi sampling
- Fresh tumor tissue during biopsy: In some cases, the testing can be performed on tumor tissue also
- Formalin-fixed paraffin-embedded solid tumor tissue (FFPE tumor tissue), often referred to as paraffin block of the tumor
- Unstained tissue slides
- Process of obtaining the sample: As outlined by the laboratory testing facility
- Preparation required: As outlined by the laboratory testing facility
- In some cases, a different source of specimen (such as peripheral blood, bone marrow biopsy specimen, or other body fluids) may be acceptable to the laboratory performing the test
- Occasionally, additional samples may be required to either repeat the test or to perform follow-up testing
- Depending on the location of testing, it may take up to 2 weeks’ turnaround time, to obtain the test results
- Many hospitals preserve the paraffin blocks for at least 7 years. In general, older paraffin blocks (over 5 years) may affect the detection of specific mutations, due to degradation of the tumor specimen over time
Cost of TRG Mutation Analysis Test:
- The cost of the test procedure depends on a variety of factors, such as the type of your health insurance, annual deductibles, co-pay requirements, out-of-network and in-network of your healthcare providers and healthcare facilities
- In many cases, an estimate may be provided before the test is conducted. The final amount may depend upon the findings during the test procedure and post-operative care that is necessary (if any)
What is the Significance of the TRG Mutation Analysis Test Result?
The presence of a mutation in the TRG gene indicates a positive result for the TRG Mutation Analysis Blood Test. This may point to a diagnosis of any of the following:
- Primary immunodeficiency
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- Many laboratories may not have the capability to perform this test. Only highly-specialized labs with advanced facilities and testing procedures may perform this test
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.
What are some Useful Resources for Additional Information?
Please visit our Laboratory Procedures Center for more physician-approved health information:
References and Information Sources used for the Article:
https://ghr.nlm.nih.gov/primer/testing/genetictesting (accessed on 05/10/2017)
https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5806a1.htm (accessed on 05/10/2017)
http://www.nature.com/gim/journal/v10/n5/full/gim200852a.html (accessed on 05/10/2017)
http://pediatrics.aappublications.org/content/106/6/1494 (accessed on 05/10/2017)
Glusman, G. (2001). Comparative genomics of the human and mouse T cell receptor loci. Immunity, 15(3), 337-49.
Leukemia Symptoms - Mayo Clinic. (2016, January 28). Retrieved from http://www.mayoclinic.org/diseases-conditions/leukemia/basics/symptoms/con-20024914
Primary immunodeficiency Symptoms - Mayo Clinic. (2015, January 20). Retrieved from http://www.mayoclinic.org/diseases-conditions/primary-immunodeficiency/basics/symptoms/con-20031958
TRG Gene - GeneCards | A0A0C4ZPA0 Protein | A0A0C4ZPA0 Antibody. (n.d.). Retrieved from http://www.genecards.org/cgi-bin/carddisp.pl?gene=TRG
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