Use of test
Mutations in the calreticulin (CALR) gene have been described in 15-25% of patients with essential thrombocythaemia (ET) and 25-35% of patients with primary myelofibrosis (PMF). As such, these are the second most common somatic mutations in these myeloproliferative neoplasms (behind JAK2 V617F).
CALR mutations have not been reported in patients with polycythaemia vera.
CALR mutation testing helps to differentiate ET/PMF from a reactive process. The presence of a CALR mutation provides strong evidence for ET or PMF; the absence of a CALR mutation does not exclude a diagnosis of ET or PMF.
There is also emerging evidence that the risk of thrombosis may be lower in patients with CALR-positive ET, and that overall survival may be improved in patients with CALR-positive PMF.
This is an assay for non-heritable mutations. It does not raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient.
Analysis of the CALR gene for the presence of exon 9 insertion or deletion mutations. Very low level CALR insertion/deletion mutations (<5% variant allele frequency) may not be detected.
Requesting the test
This test is usually requested by a haematologist or oncologist.
CALR mutation testing can be requested along with JAK2 V617F, or following a negative JAK2 result, in patients with suspected ET or PMF.
It can be carried out on an EDTA peripheral blood sample, or an EDTA bone marrow sample.
1.0 mL bone marrow in dedicated EDTA or 4 mL peripheral blood in dedicated EDTA.
To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.
We recommend that the patient or another adult check the labelling of request forms and sample tubes.
10 business days.
This test is not rebated by Medicare. The laboratory assumes that the patient or client has provided informed financial consent for the test.