The International Working Group for Myeloproliferative Research and Treatment (IWG-MRT) has provided criteria for Post-Polycythemia Vera Myelofibrosis.

Required criteria:

(1) previous diagnosis of polycythemia vera by WHO criteria

(2) bone marrow fibrosis (Grade 2 or 3 on a 0 to 3 scale; Grade 3 or 4 on a 0 to 4 scale)


Additional criteria:

(1) anemia or sustained loss of need for phlebotomy in the absence of cytoreductive therapy

(2) peripheral blood smear show leukoerythroblastic picture

(3) one or more constitutional findings (unexplained fever > 37.5°C; night sweats; > 10% unintended weight loss in 6 months)

(4) increasing splenomegaly (either newly palpable splenomegaly OR >= 5 cm increase in palpable splenomegaly).



• Palpable splenomegaly is measured as the distance from the tip of the spleen to the left costal margin.


The diagnosis of post-polycythemia vera myelofibrosis is made with:

(1) both require criteria

(2) 2 or more additional criteria

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