Test Details: The calreticulin (CALR) gene is responsible for making a protein called calreticulin which is involved in functions such as ensuring the correct folding of new proteins, maintaining correct calcium levels in cells etc. Mutations of the CALR gene are associated with bone marrow neoplasms that cause the production of excessive blood cells. They are present in about 20-25% of adults with ET and 25-30% of adults with PMF. This DNA-based cascading reflex identifies the disease-defining mutations in four genes used for diagnosis and follow-up of myeloproliferative neoplasms (MPNs) including polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF) and chronic neutrophilic leukemia (CNL). The reflexed assays test leukocytes from blood or bone marrow aspirates for clinically relevant hotspot mutations using an advanced DNA sequencing method.