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Test Code MISC2MAYOKITVS KIT Asp816Val Mutation Analysis, Varies


Specimen Required


Submit only 1 of the following specimens:

 

Specimen Type: Peripheral blood

Container/Tube: Lavender top (EDTA) or yellow top (ACD)

Specimen Volume: 3 mL

Collections Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube. Do not aliquot.

3. Label specimen as blood.

Specimen Stability: Ambient (preferred) 7 days/Refrigerate 7 days

 

Specimen Type: Bone marrow

Container/Tube: Lavender top (EDTA) or yellow top (ACD)

Specimen Volume: 2 mL

Collections Instructions:

1. Invert several times to mix bone marrow.

2. Send specimens in original tube. Do not aliquot.

3. Label specimen as bone marrow.

Specimen Stability: Ambient (preferred) 7 days/Refrigerate 7 days

 

Specimen Type: Extracted DNA from blood or bone marrow

Container/Tube: 1.5- to 2-mL tube

Specimen Volume: Entire specimen

Collection Instructions:

1. Label specimen as extracted DNA from blood or bone marrow.

2. Provide indication of volume and concentration of DNA.

Specimen Stability Information: Frozen (preferred)/Refrigerated/Ambient


Forms

1. Hematopathology Patient Information (T676) in Special Instructions

2. If not ordering electronically, complete, print, and send a Hematopathology/Cytogenetics Test Request (T726)) with the specimen.

Secondary ID

607981

Method Name

Allele-Specific Oligonucleotide Polymerase Chain Reaction (PCR)

Reporting Name

KIT Asp816Val Mutation Analysis, V

Specimen Type

Varies

Specimen Minimum Volume

Blood, Bone Marrow: 1 mL
Extracted DNA: 50 mcL at 20 ng/mcL concentration

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Reject Due To

Gross hemolysis Reject
Moderately to severely clotted
Bone marrow biopsies
Paraffin-embedded bone marrow clots
Paraffin-embedded tissue
Slides
Paraffin shavings
Reject

Clinical Information

Systemic mastocytosis is a hematopoietic neoplasm that can be included in the general category of chronic myeloproliferative disorders (CMPD). These neoplasms are characterized by excessive proliferation of 1 or more myeloid lineages, with cells filling the bone marrow and populating other hematopoietic sites. In systemic mastocytosis, mast cell proliferation is the defining feature, although other myeloid lineages and B cells are frequently part of the neoplastic clone.

 

Function-altering point alterations in KIT, a gene coding for a membrane receptor tyrosine kinase, have been found in myeloid lineage cells in the majority of systemic mastocytosis cases. The most common KIT alteration is an adenine to thymine base substitution (A>T) at nucleotide position 2447, which results in an aspartic acid to valine change in the protein (Asp816Val). Much less frequently, other alterations at this same location are found, and occasional cases with alterations at other locations have also been reported. Variations at codon 816 are believed to alter the protein such that it is in a constitutively activated state. The main downstream effect of KIT activation is cell proliferation.

 

Detection of a variant at codon 816 is included as one of the minor diagnostic criteria for systemic mastocytosis in the World Health Organization classification system for hematopoietic neoplasms and is also of therapeutic relevance, as it confers resistance to imatinib, a drug commonly used to treat CMPD. It is now clear that individual mast cell neoplasms are variable with respect to the number of cell lineages containing the variant; some having positivity only in mast cells and others having positivity in additional myeloid and even lymphoid lineages. The alteration has not been reported in normal tissues.

Reference Values

An interpretive report will be provided indicating the mutation status as positive or negative.

Interpretation

The test will be interpreted as positive or negative for KIT Asp816Val.

Method Description

This assay detects the KIT alteration responsible for Asp816Val. The technique used is allele-specific oligonucleotide polymerase chain reaction (ASO-PCR) with fragment analysis on a genetic analyzer. DNA is extracted from bone marrow or blood and PCR is used to amplify across the alteration site in 2 separate tubes; 1 contains a reverse primer complementary to the unaltered sequence and the other contains a reverse primer complementary to the altered sequence. Each of these is labeled with a fluorescent tag and contains an identical, non-labeled forward primer. Both primer sets amplify a 200-bp fragment that differs only at the alteration site. The unaltered fragment should be amplified in all samples. Samples negative for KIT Asp816Val will not have an amplified fragment in the altered sequence reaction tube. Positive samples will have amplified fragments in both tubes. The test gives a qualitative (positive or negative) result only, as the end point PCR used is not reliable for quantification.(Unpublished Mayo method)

Performing 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. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

81273

LOINC Code Information

Test ID Test Order Name Order LOINC Value
KITVS KIT Asp816Val Mutation Analysis, V 55201-8

 

Result ID Test Result Name Result LOINC Value
MP055 Specimen Type 31208-2
607982 Interpretation 69047-9
607983 Signing Pathologist 19139-5

Day(s) Performed

Monday through Friday

Report Available

4 to 7 days