Polymerase Chain Reaction (PCR) and Fragment Analysis
CALR
Calreticulin
Essential Thrombocythemia
JAK2-negative Myeloproliferative Neoplasm
Myelofibrosis
Myeloproliferative Disorder
Myeloproliferative Neoplasm (MPN)
Primary Myelofibrosis
Bone Marrow
Specimen must arrive within 7 days of collection.
The following information is required:
1. Pertinent clinical history
2. Clinical or morphologic suspicion
3. Date of collection
4. Specimen source
Container/Tube: Lavender top (EDTA) or yellow top (ACD solution B)
Specimen Volume: 2 mL
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.
1 mL
Gross hemolysis | Reject |
Moderately to severely clotted | Reject |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Bone Marrow | Ambient (preferred) | 7 days | |
Refrigerated | 7 days |
Mutations in the JAK2, CALR and MPL genes are considered driver events in the BCR-ABL1 negative myeloproliferative neoplasms (MPN) including polycythemia vera (PV), primary myelofibrosis (PMF) and essential thrombocythemia (ET). The JAK2 V617F mutation occurs in 95% to 98% of patients with PV, 50% to 60% of patients with PMF and 50% to 60% of patients with ET respectively at diagnosis. Other JAK2 mutations in exon 12 to 15 occur in the remaining patients with PV. Mutations in the CALR gene occur in 20% to 30% of patients with PMF and 20% to 30% of patients with ET at diagnosis. A 52 base pairs (bp) deletion (53%) and a 5 bp deletion (32%) are the most common mutations in the CALR gene while other types of mutations may occur in the remaining cases. MPL exon 10 mutations occur in 5% to 10% of patients with PMF and 5% to 10% of patients with ET. Mutations in JAK2, CALR and MPL are mutually exclusive. The JAK2 V617F mutation is detected by quantitative polymerase chain reaction (qPCR). The CALR mutations are detected by PCR targeting the exon 9. The MPL mutations in exon 10 are detected by Sanger sequencing. All mutations in JAK2, CALR and MPL can also be detected by next generation sequencing (NGS). In addition to the mutations in JAK2, CALR and MPL, mutations in many other genes including ASXL1, TET2, DNMT3A, SRSF2, SF3B1, U2AF1, ZRSR2, EZH2, IDH1, IDH2, CBL, KRAS, NRAS, STAG2, and TP53 can occur in MPN. These additional mutations are more frequent in PMF and advanced disease, as compared to PV and ET. It is known that mutations in the ASXL1, SRSF2, U2AF1, EZH2, IDH1 and IDH2 are correlated with a poor prognostic risk. While a single gene test on JAK2, CALR and MPL can be clinically useful, all above mentioned gene mutations can be detected by NGS.
An interpretive report will be provided.
An interpretive report will be issued.
The results will be reported as 1 of the 3 states if DNA amplification is successful (see Cautions):
-Positive. A deletion-insertion-type mutation was detected in CALR, exon 9.
-Negative. No deletion or insertion was detected in CALR, exon 9.
-Equivocal. A small amplicon suspicious for a deletion-insertion type mutation was detected in CALR, exon 9.
Positive mutation status is highly suggestive of a myeloid neoplasm but must be correlated with clinical and other laboratory and morphologic features for definitive diagnosis.
Negative mutation status does not exclude the presence of a myeloproliferative neoplasm or other neoplastic disorders.
A positive result is not specific for a particular myeloproliferative neoplasm (MPN) diagnosis, and clinicopathologic correlation is necessary in all cases.
A negative result does not exclude the presence of MPN or other neoplastic processes.
This test is a fragment analysis assay and only detects deletions-insertions (delins). It will not detect point mutations. However, all reported disease-causing mutations in MPN described to date are insertions and/or deletions.
This test may not differentiate between out-of-frame and in-frame delins in rare cases. However, in-frame delin mutations are very rare (<0.5%) and have only been reported in few healthy individuals and myeloproliferative neoplasm patients with JAK2V617F mutation or out-of-frame CALR mutation. Most of the rare in-frame delins are considered germline variants and represent benign alterations (ie, polymorphisms).
Infrequently, amplification failure can be encountered in a sample, due to inadequate DNA, poor DNA quality, or a polymerase chain reaction inhibitor. In these circumstances, the assay will be reattempted and if persistently unsuccessful, the report will be issued with an "Invalid" result.
1. Klampfl T, Gisslinger H, Harutyunyan AS, et al. Somatic mutation of calreticulin in myeloproliferative neoplasms. N Engl J Med. 2013;369(25):2379-2390
2. Rumi E, Pietra D, Ferretti V, et al. JAK2 or CALR mutation status defines subtypes of essential thrombocythemia with substantially different clinical course and outcomes. Blood. 2014;123(10):1544-1551
3. Greenfield G, McMullin MF, Mils K. Molecular pathogenesis of the myeloproliferative neoplasms. J Hematol Oncol. 2021;14(1):103
4. Khoury JD, Solary E, Abla O, et al. The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms. Leukemia. 2022;36(7):1703-1719. doi:10.1038/s41375-022-01613-1
Polymerase chain reaction (PCR) amplification of CALR exon 9 is performed on DNA isolated from the patient sample. The PCR product is then run on an ABI 3130xl Genetic Analyzer for fragment analysis to detect insertions and deletions. An unmutated CALR will show an amplicon at 266 base pairs (bp), a mutated CALR with insertion will show an amplicon greater than 266 bp, and a mutated CALR with deletion will show an amplicon smaller than 266 bp. This assay has an analytical sensitivity of approximately 6% (ie, 6 mutation-containing cells in 100 total cells) in most mutation types, except for the rare type of 1-bp deletion, which has a sensitivity of approximately 20%.(Unpublished Mayo method)
Monday through Friday
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.
81219
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
CALFM | CALR Gene Mutation, Exon 9, BM | 77174-1 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
618655 | Final Diagnosis | 69047-9 |
618656 | Method | 85069-3 |
618657 | Signing Pathologist | 18771-6 |
618659 | Additional Information | 48767-8 |
618660 | Disclaimer | 62364-5 |