Isocitrate dehydrogenase enzyme isoforms 1 (IDH1) and 2 (IDH2) are nicotinamide adenine dinucleotide phosphate (NADP)-dependent isocitrate dehydrogenases that catalyze the oxidative decarboxylation of isocitrate to produce alpha-ketoglutarate in normal cell metabolism. Mutation in IDH1 or IDH2 is mutually exclusive and appears to be an early event in the development of certain tumors that impairs normal enzyme activity, resulting in loss of the ability to catalyse conversion of isocitrate to alpha-ketoglutarate. However, as a result, the mutated isoforms now acquire a neomorphic activity able to catalyze the NADPH-reduction of alpha-ketoglutarate to R(-)-2-hydroxyglutarate (2HG), a presumed oncometabolite. While no therapies directly targeting IDH1 or IDH2 mutated proteins are currently approved, cells that accumulate 2HG may have altered epigenetic regulation due to hypermethylation and as a result be sensitive to DNA methyltransferase inhibitors. The presence of an IDH1 or IDH2 mutation has both diagnostic and prognostic significance in central nervous system (CNS) tumors and prognostic value in hematologic disorders, such as myelodysplastic syndrome or acute myeloid leukemia.

Mutations in isocitrate dehydrogenase enzyme isoform 1 (IDH1) and, to a lesser extent (5-10% of all IDH mutation), isoform 2  (IDH2) genes have been identified in a large proportion of diffuse astrocytomas (70‐90%), oligodendrogliomas (69‐94%), oligoastrocytomas (78‐100%), and secondary glioblastomas (82‐88%). Additionally, these mutations have been found to be associated with a younger age (<55 years old) among cases of adult diffuse astrocytomas, WHO grade III astrocytomas, and glioblastomas. IDH1mutations are only rarely reported among pilocytic astrocytomas, primary gliomas, supratentorial primitive neuroectodermal tumors and pleomorphic xanthoastrocytomas. IDH1 and IDH2 are absent in pediatric diffuse astrocytomas, ependymomas, medulloblastomas, primitive neuroectodermal tumors, dysembryoblastic tumors and are not found in non‐neoplastic conditions that can often mimic gliomas (e.g. changes caused by radiation, viral infections, infarctions, etc.). In general, patients with CNS tumors harboring IDH1 and IDH2 mutations have a better prognosis based on increased overall survival. 

Similar to CNS tumors, mutation in IDH1 or IDH2 serves as a prognostic factor in certain hematopoetic malignancies.  However, in contrast to CNS tumors, IDH1 and IDH2 mutations have generally been associated with more unfavorable outcomes and shorter overall survival, particularly in cases of myelodysplastic syndrome and acute myeloid leukemia with a normal cytogenetic karyotype that lack FLT3 or NPM1 mutations. 

Extracted nucleic acid specimens may occasionally be received in cases where no primary sample is available for testing.  All nucleic acid specimens received for testing must have been extracted in a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by the CAP and/or the CMS.

Batched runs begin Monday or first working day of each week and Wednesday of each each week

FFPE tissue - The percentage of tumor in the specimen should be ≥20%. specimens with <20% tumor will be evaluated on a case by case basis to determine whether macro-dissection is possible based on the dispersal of cells.

A documented prior authorization will need to be present in Health Link before testing can be performed. 

The ordering source should consult the Genetic Testing at UW Health Clinical Laboratories document on U-Connect prior to ordering testing. Contact UWHC Referral office (608) 262-6388 for questions. 

Three slides each containing 5 microns (uM) of FFPE tissue should be sent. Second slide should be H&E stained with the tumor circled. Please indicate percent tumor on the H&E. 

If an add-on order is needed, please contact UWHC Surgical Pathology at (608)263-8443. A Surgical Pathology Tissue Examination Request form will need to be completed and faxed to (608)262-7174.

Blood/Bone Marrow Aspirate - Whole Blood. Do not centrifuge or freeze.

In order to ensure that molecular testing is conducted on a representative sample and a direct correlation of molecular results with morphologic findings is possible, a pathologist selects the specimen(s) and, whenever possible, identifies the suspicious or neoplastic cells submitted for molecular testing.

Transport with a cold pack. Avoid excessive heat.

Transport at room temperature or with a cold pack. Avoid excessive heat.

Specimens processed in alternative fixatives.

A written interpretive report is provided by the laboratory detailing all genetic variants detected and genes in the panel. The significance of genetic variants to pathogenicity and therapeutic response will be indicated whenever possible.

A "Not Detected" result may be due to either insufficient tissue or tumor present in the sample, tumor heterogeneity, to the presence of inhibitors or to bias or inefficiencies in PCR amplification. The four genes covered are not all sequenced in their entirety. Mutations outside the amplicons will not be detected. The limit of detection of this assay is estimated to be 5% at 500X coverage and 10% at 200X coverage and mutations below 100X coverage cannot reliably be detected. This technology cannot detect large insertions, deletions, duplications or genomic copy number variants. Rare or complex polymorphisms may be present that could lead to false negative or positive results.

This test cannot differentiate between somatic or germline genetic variants. Additional testing may be necessary to clarify the significance of results if there is a potential for hereditary risk. It is recommended that patients receive genetic consultation where appropriate, to explain the implications of this test result, including probabilistic risk of disease and uncertainties, and the reproductive or medical options it raises. Test results should be interpreted in the context of clinical findings, tumor sampling, histopathology, and all other laboratory data. The presence or absence of cancer associated mutations does not guarantee either a positive or negative response to therapy. All test results should be interpreted in the context of patient's clinical presentation.

A "Detected" results indicates the presence of a variant. This test should not be used as the only criterion to form a clinical conclusion, instead, results should be correlated with other test results, patient symptoms and clinical presentation.

The variants nomenclature used is recommended by the Human Genome Variation Society (http://www.hgvs.org/mutnomen/).

The performance characteristics of this test were validated by UWHC Clinical Laboratories. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test; however, FDA approval or clearance is currently not required for clinical use of this test. The UWHC Clinical Laboratories is authorized under Clinical Laboratory Improvement Amendments (CLIA) to perform high-complexity testing.

A professional fee is associated with this test (CPT Code G0452).