Repeat JAK2 V617F testing in patients with suspected essential thrombocythaemia.

Molecular investigation for characteristic initiating mutations, in addition to clinical, haematological and histopathological evidence, has become an integral part of myeloproliferative neoplasm (MPN) diagnosis. Detection of the JAK2 V617F mutation and those within CALR exon 9, MPL exon 10 and JAK2 exon 12 can be performed by a variety of methodologies each possessing its own characteristics of sensitivity, specificity and clinical applicability.1 Mutation identification has been traditionally performed in a logical, stepwise fashion guided by other presenting features or increasingly in a simultaneous manner by next-generation sequencing (NGS). Up to 15% of patients with MPN of essential thrombocythaemia (ET) have no evidence of the canonical mutations (termed ‘triple-negative’) and are associated with a distinct clinical course particularly in regard to thrombotic risk therefore influencing treatment.2 Low JAK2 V617F allele burdens are by themselves insufficient to result in a diagnosis of an MPN in the absence …