Barbui et al compared survival for a patient with essential thrombocythemia (ET) versus early primary myelofibrosis (PMF). Distinguishing the two by careful adherence to the WHO histologic criteria is important for determining the patient's prognosis. The authors are from the University of Pavia, S. Bortolo Hospital in Vicenza, the University of Padua, the University of Florence, the University of Cologne, the Medical University of Vienna and the Mayo Clinic.
Features that ET and prefibrotic PMF may have in common:
(1) thrombocytosis
(2) positive clonal markers (JAK2 or MPL)
Parameters associated with death:
(1) histologic diagnosis (ET vs PMF)
(2) age in years at presentation
(3) history of thrombosis
(4) leukocyte count
(5) hemoglobin
Parameter
Finding
Hazard Ratio
histologic diagnosis
essential thrombocythemia
1
primary myelofibrosis
1.6
age in years
<= 60 years
1
> 60 years
6.7
history of thrombosis
no
1
yes
2.8
leukocyte count
<= 11,000 per µL
1
> 11,000 per µL
2
hemoglobin
>= 12 g/dL
1
< 12 g/dL
3
where:
• The cutoff for anemia was adjusted for gender.
cumulative hazard ratio for death =
= PRODUCT(hazard ratios for the 5 parameters)
The distinction of prefibrotic myelofibrosis from essential thrombocythemia is of limited significance when considering survival. However, it is more important when considering leukemia transformation (hazard ratio 4.5).
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