Peripheral Blood: 5 mL in EDTA tube.</p>
Testing proceeds by reflex, with the next step triggered by a negative result or a weakly positive result of uncertain clinical significance; no further testing is performed once an informative result is obtained. <br><br>
Testing is performed on plasma for increased sensitivity whenever possible. <br><br>
Test Customization: Tests may also be ordered individually. </p>
The JAK2 V617F mutation has been reported in >80% of the patients with polycythemia vera (PV), 30-50% of patients with either essential thrombocythemia (ET) or primary myelofibrosis (PMF). This mutation is not detected in normal individuals. A small subset of patients with myeloproliferative neoplasms (MPN) that are negative for the JAK2 V617F mutation will harbor JAK2 mutations in exon 12. More rare mutations are detected in exons 13 and 14. JAK2 exon 12 mutations have been associated with erythrocytosis and atypical bone marrow morphology. JAK2 mutations can be used to differentiate reactive conditions from neoplastic processes.
MPL W515 and S505 mutations are present in JAK2 negative patients with primary myelofibrosis (PMF) or essential thrombocythemia (ET) at a frequency of approximately 1-5%. The MPL S505 mutation is usually detected in patients with familial essential thrombocythemia. Calreticulin (CALR) is endoplasmic reticulum protein that binds calcium and plays a role in signaling and protein expression. It is also found in the nucleus and believed to play a role in transcription regulation.
Somatic insertions or deletions in exon 9 of CALR gene are detected in 67% of JAK2/MPL negative essential thrombocythemia (ET) and 88% of JAK2/MPL negative primary myelofibrosis (PMF) patients. CALR mutations are not detected in polycythemia vera (PV) patients. CALR mutations appear to be mutually exclusive of JAK2 and MPL mutations. It has been reported that patients with mutated CALR have a lower risk of thrombosis and longer overall survival than patients with JAK2 mutation.