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HelpTest Code IDHQ IDH1 (R132) and IDH2 (R140 and R172) Quantitative Detection, Droplet Digital PCR, Varies
Shipping Instructions
1. Refrigerated specimens must arrive within 14 days of collection, and ambient specimens must arrive within 7 days of collection.
2. Collect and package specimen as close to shipping time as possible.
Necessary Information
The following information is required:
1. Pertinent clinical history
3. Specimen source (blood or bone marrow)
Specimen Required
Submit only 1 of the following specimens
Specimen Type: Whole blood
Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Yellow top (ACD-B) or green top (heparin)
Specimen Volume: 4mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
3. Label specimen as blood.
Specimen Stability: Refrigerated 14 days/ Ambient 7 days
Specimen Type: Bone marrow aspirate
Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Yellow top (ACD-B) or green top (heparin)
Specimen Volume: 2mL
Collection Instructions:
1. Invert several times to mix bone marrow.
2. Send bone marrow specimen in original tube. Do not aliquot.
3. Label specimen as bone marrow.
Specimen Stability: Refrigerated 14 days/ Ambient 7 days
Specimen Type: Extracted DNA from blood or bone marrow
Container/Tube: 1.5- to 2-mL tube with indication of volume and concentration of DNA
Specimen Volume: Entire specimen
Collection Instructions:
1. Label specimen as extracted DNA and source of specimen
2. Indicate volume and concentration of DNA on label. The required volume of DNA is at least 50 mcL at a concentration of 50 ng/mcL
Specimen Stability: Frozen (preferred)/Refrigerated
Forms
1. Hematopathology Patient Information (T676)
2. If not ordering electronically, complete, print, and send an Hematopathology/Cytogenetics Test Request (T726) with the specimen.
Useful For
Detecting IDH1 R132 and IDH2 R140 and R172 mutations in acute myeloid leukemia patients at the time of diagnosis to guide targeted therapy
Monitoring minimal residual disease during the clinical and therapeutic course
Genetics Test Information
A highly sensitive quantitative assay for the detection of 6 IDH1 R132 mutations (R132H, R132S, R132C, R132G, R132P, and R132L) and 10 IDH2 mutations R140 (R140Q, R140L, R140G, R140W) and R172 (R172K, R172M, R172G, R172S[G>C], R172S[G>T], R172W).
Special Instructions
Method Name
Droplet Digital Polymerase Chain Reaction (ddPCR)
Reporting Name
IDH1 and IDH2, Quant, ddPCR, VSpecimen Type
VariesSpecimen Minimum Volume
Whole blood: 4mL
Bone marrow: 2mL
Extracted DNA: 50 mcL at 50 ng/mcL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Refrigerated (preferred) | 14 days | |
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | Reject |
| Moderately to severely clotted | Reject |
Clinical Information
Isocitrate dehydrogenase 1 (IDH1) is a cytosolic/peroxisomal enzyme involved in citric acid cycle and other cellular metabolic processes. It catalyzes the oxidative decarboxylation of isocitrate to alpha-ketoglutarate (a-KG), generating reduced nicotinamide adenine dinucleotide phosphate (NADPH) from NADP(+). Isocitrate dehydrogenase 2 (IDH2) is a mitochondrial NADP(+)-dependent enzyme that catalyzes the oxidative decarboxylation of isocitrate to a- KG, generating NADPH from NADP(+). Mutations in codon R132 of IDH1 or R140 or R172 in IDH2 confer an abnormal enzyme activity that converts a-KG to D-2- hydroxyglutarate (2-HG) resulting in elevation of 2-HG and a hypermethylation state, associated in myeloid neoplasms including acute myeloid leukemia (AML). IDH1 and IDH2 point mutations are seen in approximately 5% to 33% de novo acute myeloid leukemia (AML) and 7% to 25% secondary AML.
The US Food and Drug Administration (FDA) has approved ivosidenib (AG-120) for the treatment of newly-diagnosed IDH1-mutated AML (patients 75 years of age and older or who have comorbidities that preclude the use of intensive induction chemotherapy) and relapsed/refractory AML in adult patients.(1) The FDA has also approved enasidenib (AG-221) for the treatment of IDH2-mutated relapsed/refractory AML.(2)
IDH1 and IDH2 have also been shown to be suitable minimal residual disease markers for AML post-therapy.
Reference Values
An interpretive report will be provided.
Interpretation
The assay is reported as positive or negative. In positive cases, the mutation and its variant allele fraction (VAF) are reported.
VAF%= (mutant copy number)/(mutant copy number + wild-type number)
The precision of this quantitative assay is excellent but interassay variability may occur such that result changes should not be considered significant if 2 single measurements differ by less than 0.5 log (3.16-folds).
Cautions
Other IDH1 or IDH2 variants outside the 16 assay targets are not detected by this assay.
Method Description
This test will be performed on Bio-Rad QX200 digital polymerase chain reaction (PCR) system. Mutation-specific droplet digital PCR probes were designed using Thermo Fisher Scientific MGB (minorgroove binder) Taqman technology. The PCR reactions for each patient are placed into an 8-tube cartridge along with droplet generation oil. The cartridge is loaded onto the droplet generator instrument to partition each reaction into 20,000 nanoliter-sized droplets.
Droplets are transferred to a plate for PCR amplification. Targets are amplified by end-point PCR in each droplet. The QX200 automated droplet reader counts every acceptable droplet and measures fluorescence emissions from each droplet using two different fluorescence channels (FAM and VIC). QuantaSoft software measures the number of negative and positive droplets for each fluorophore in each sample. Poisson statistics are used to determine the concentration of mutant and wild type copies in the sample.(Unpublished Mayo method)
Day(s) Performed
Monday through Saturday
Report Available
4 to 8 daysSpecimen Retention Time
Blood/bone marrow: 2 weeks; Extracted DNA: 3 monthsPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
81120
81121
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| IDHQ | IDH1 and IDH2, Quant, ddPCR, V | 95772-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| MP063 | Specimen Type | 31208-2 |
| 618389 | Interpretation | 69047-9 |
| 618390 | Signing Pathologist | 18771-6 |