Key differences from the 2011 diagnostic recommendations included: lower threshold values for hemoglobin and hematocrit and bone marrow examination for diagnosis of polycythemia vera (PV), according to the revised WHO criteria; the search for complementary clonal markers, such as ASXL1, EZH2, IDH1/IDH2, and SRSF2 for the diagnosis of myelofibrosis (MF) in patients who test negative for JAK2V617, CALR or MPL driver mutations.
For essential thrombocythemia, reported risk factors for leukemic transformation include advanced age, extreme thrombocytosis, anemia, leukocytosis, and sequence variants/mutations involving TP53 and EZH2 (for expansion of gene symbols, see www.genenames.org); for polycythemia vera, advanced age, leukocytosis, abnormal karyotype, mutations involving SRSF2 and IDH2, and treatment with pipobroman, chlorambucil, or P32; and for PMF, increased blast percentage, thrombocytopenia, abnormal karyotype, triple-negative driver mutational status, and sequence variants/mutations involving SRSF2, RUNX1, CEBPA, and SH2B3.
Additionally, chromatin modification genes (ASXL1 and EZH2) were frequently mutated in PMF patients (0·50) and, to a significantly lesser extent, in ET (0·13) and PV (0·07).