Test Details: The majority of patients with polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF) have a mutation in the JAK2, CALR, or MPL gene and genetic testing is an important tool for the classification and diagnosis of these disorders. The samples are first tested for Jak2 Ex14 mutation- V617F and if negative tested for the Exon 12 mutations. acquired mutations in the transmembrane-juxtamembrane region of MPL (MPLW515 mutations) have been reported in approximately 5% of JAK2V617F-negative PMF and about 1% of all cases of ET. Calreticulin (CALR) gene encodes a protein called calreticulin which is associated with protein folding, calcium level maintenance in cells and many other cell functions. Mutations in CALR causes excessive production of blood cells, leading to disorder known as Myeloproliferative Neoplasms (MPNs).