What are other Names for this Test? (Equivalent Terms)

• D2HGA2 Mutation Analysis Test
• IDHP_HUMAN Mutation Analysis Test
• Isocitrate Dehydrogenase 2 (NADP+), Mitochondrial Mutation Analysis Test

What is IDH2 Mutation Analysis Test? (Background Information)

• IDH2 mutation refers to an alteration in the IDH2 gene, which is associated with cancers of the brain, blood vessels, and other organs.
• The IDH2 gene gives instructions for a protein called isocitrate dehydrogenase 2 (IDH 2). The IDH 2 protein is an enzyme important in cellular metabolism for the role it plays in a crucial biochemical process called the Krebs cycle
• The Krebs cycle generates the vast majority of energy for cells. As part of this cycle, IDH 2 helps convert a compound, called isocitrate, into another called alpha-ketoglutarate through a dehydration reaction, and hence, the name isocitrate dehydrogenase
• NADPH, another product of the action of IDH 2, is necessary for the breakdown of fats for energy. It also helps protect cells from dangerous compounds called reactive oxygen species
• Alterations in the IDH2 gene may result in the formation of an IDH 2 protein that is defective. IDH 2 produced from a mutated IDH2 gene is unable to perform catalytic function in the Krebs cycle of cells
• Cells of the nervous system, called neurons, are especially susceptible to the harmful effects of defective IDH enzymes. These harmful effects include the transformation of healthy neurons into cancerous ones
• It is unknown why IDH2 gene mutations may cause cancer. However, it may be because of neurons’ high metabolic activities and particular reliance on fats for proper function, both of which are significantly disturbed by defective IDH 2
• Another possible cancer-causing mechanism is the buildup of reactive oxygen species due to a decrease in the NADPH that is produced. Reactive oxygen species may damage DNA and lead to a cell becoming cancerous
• The IDH2 Mutation Analysis Test is a genetic test that detects abnormalities in the IDH2 gene. It is used to diagnose cancers of the nervous, circulatory, musculoskeletal, and various other systems. The test also aids in the treatment of cancer by guiding selection of therapeutic drugs, including disqualifying certain drugs from use

The molecular testing, in general, can be performed using a variety of methods. Some of these methods include:

• In situ hybridization technique, 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 IDH2 Mutation Analysis Test?

Following are the clinical indications for performing the IDH2 Mutation Analysis Test:

• Delayed development
• Weak muscle tone (hypotonia)
• Pain that may worsen at night or during physical activity
• Swelling in the painful area; presence of a lump or mass
• Enlargement of an existing growth
• Limping
• Difficulty moving the affected limb
• Changes in urination (for pelvic tumors)
• Headache
• Nausea or vomiting
• Confusion or a decline in brain function
• Memory loss
• Personality changes or irritability
• Difficulty with balance (ataxia)
• Urinary incontinence
• Vision problems, such as blurred vision, double vision or loss of peripheral vision
• Speech difficulties
• Seizures, especially in someone without a history of seizures

In general, the molecular genetic testing is undertaken in the following situations:

• To assist (and in some cases, confirm) the initial diagnosis
• To distinguish other tumors/conditions that have similar histological features, when examined by a pathologist under the microscope
• 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 IDH2 Mutation Analysis Test?

Following is the specimen collection process for IDH2 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:
  • Fresh tumor tissue during biopsy
  • 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

Note:

• 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 IDH2 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 IDH2 Mutation Analysis Test Result?

A mutation in the IDH2 gene indicates a positive result for the IDH2 Mutation Analysis Test. This may point to a diagnosis of any of the following:

• 2-Hydroxyglutaric aciduria
• Glioma
• Cholangiocarcinoma
• Chondrosarcoma
• Cytogenically normal acute myeloid leukemia (CN-AML)
• Maffucci syndrome
• Ollier disease
• Primary myelofibrosis

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:

• IDH2 mutation most notably occurs in a location of the chromosome called 15q26.1 i.e., the long arm (q) of chromosome 15 in position 26.1
• IDH, a similar protein, is encoded by the IDH1 gene. In contrast to IDH, which is present in the cellular matrix within cells (cytoplasm), IDH 2 is present in the mitochondria of cells
• 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.

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/brain-cancer/

Please visit our Laboratory Procedures Center for more physician-approved health information:

http://www.dovemed.com/common-procedures/procedures-laboratory/