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Dec 8, 2017

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IDH1/IDH2 Mutation Analysis

IDH1/IDH2 Mutation Analysis (IDH-M) Molecular Diagnostics Lab Test

Name: IDH1/IDH2 Mutation Analysis

Test Name: IDH1/IDH2 Mutation Analysis

Health Link Test Code: IDH-M

LIS Test Code: IDH-M

CPT Code(s): 81403 (IDH1), 81403 (IDH2)

Methodology: Mass Spectrometry

Clinical Information:

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. 

Days Performed: Mon, Wed.

In-Lab Turnaround Time: 10 days.

Specimen: Formalin-fixed, paraffin embedded tissue, whole blood or bone marrow aspirate

Collection Container: Lavender top

Collection Instructions:

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

 

Provider must contact patient’s insurance about coverage for this molecular test and then counsel the patient on out-of-pocket costs.

 

For Unity and WI-MA patients, documented prior authorization will need to be present in Health Link or sent to laboratory before test will be collected and/or performed.

 

For all other managed care plans, referral must be placed in Health Link in order for testing on tissue or bone marrow specimens to be performed at UW Health; and patients should be referred to their primary care physician for collection of blood specimens.

 

For any other insurers, providers must check with insurer before ordering testing.

Collection Volume: 1 mL

Pediatric Collection Volume: 0.6 mL

Stability Ambient:

Indefinitely

Stability Refridgerated:

Indefinitely

Stability Frozen:

Not acceptable

Sample Analyzed: Tissue, whole blood, or bone marrow

Testing Volume: 1 mL

Pediatric Testing Volume: 0.6 mL

Specimen Processing:

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 Intra-Lab Send-Out Form.

 

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.

Outreach Specimen Processing:

Transport with a cold pack. Avoid excessive heat.

Specimen Transport:

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

Unacceptable Criteria:

Specimens processed in alternative fixatives.

Interpretation:

A written interpretive report is provided by the laboratory.

 

This method is qualitative. Codons assessed: IDH1 (R132), IDH2 (R140 and R172)

Not Detected - variant in specified codon was not detected.

Detected - variant in specified codon was detected.

 

FFPE tissue sections of tumors and representative blood/cell/bone marrow specimens are selected and reviewed by a pathologist or a hematopathologist, respectively. Relevant FFPE tumor tissue is macro-dissected for mutational analysis. Following de-paraffinization of the tissue and receipt of blood/cell/bone marrow specimens, genomic DNA is isolated by automated nucleic acid extraction. Polymerase chain reaction (PCR) is used to amplify across regions of the IDH1 (codon 132) and IDH2 (codons 140 and 172) genes.  Following PCR, detection of mutations in codon 132 of IDH1 and codons 140 and 172 of IDH2 is accomplished through a series of primer extension reactions in which the resultant products are analyzed using a MassARRAY® System with Chip prep module (Agena Bioscience; San Diego, CA USA)

 

 Approximately 90% of all IDH mutations occur in codon 132, exon 4 of the IDH1 gene, and less frequently, in codons 140 and 172, exon 4 of the IDH2 gene.  Consequently, this test was validated to qualitatively detect mutations in codon 132 of IDH1 (R132H, R132C, R132S, R132G, R132H and R132V) and mutations in both codon 140 (R140Q and R140L) and 172 (R172M and R172K) in IDH2 in DNA extracted from formalin-fixed, paraffin embedded (FFPE) tissue, fresh/frozen tissue, peripheral blood and bone marrow specimens. The analytical sensitivity of the assay has been established to be ~10%.  Consequently, IDH1 (codon 132) and IDH2 (codons 140 and 172) mutations present in cells at <10% may not be detected.  Moreover, detection of IDH1 (codon 132) and IDH2 (codons 140 and 172) mutations depend on numerous factors including, but not limited to, the integrity and heterogenous nature of tissue/tumor samples, the presence/absence of PCR inhibitors and/or the presence/absence of other proximal mutations and/or DNA sequence polymorphisms in IDH1 and IDH2. Test results should not be used as the only criterion to form a clinical conclusion, but should be interpreted in the context of all clinical findings, tumor sampling and laboratory data.

Interpretation Type: Expected Results

Test Limitations:

The lower limit of detection for tumor DNA in a normal DNA background is approximately 5-10%.

Additional Information:

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 results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. 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.