Significant increase in the apparent incidence of essential thrombocythemia related to new WHO diagnostic criteria: a population-based study

To observe the effect of the new World Health Organization (WHO) criteria on the incidence of myeloproliferative neoplasms, we performed a retrospective study of a population-based registry in the Côte d’Or area, France, from 1980 to 2007. A total of 524 myeloproliferative neoplasms were registered for the 1980–2007 period, including 135 polycythemia vera, 308 essential thrombocythemia and 81 idiopathic myelofibroses. No change in the incidence of either polycythemia vera or idiopathic myelofibrosis was observed for the 2005–2007 period, compared to 1980–2004. On the contrary, a pronounced increase in the incidence of essential thrombocythemia was noted after 2005, mainly due to the use of JAK2 mutation screening and a lower threshold of platelet count. Our study confirms the relevance of the new WHO diagnostic criteria in allowing earlier diagnosis of essential thrombocythemia

Clinical value of the quantitative expression of the three epitopes of CD34 in 300 cases of acute myeloid leukemia.

BACKGROUND AND OBJECTIVES: The various epitopes of the CD34 molecule have been classified according to their different sensitivities to enzymatic cleavage by neuraminidase, chymopapain and a glycoprotease from Pasteurella haemolytica. Although monoclonal antibodies have been developed that specifically identify these epitopes, few studies have evaluated the distribution and quantitative expression of such epitopes on leukemic blasts. DESIGN AND METHODS: We report here a prospective multicenter study in which we examined and quantified the expression of the 3 classes of CD34 on fresh leukemic blast cells from 300 cases of acute myeloid leukemia (AML). The binding of monoclonal antibodies was studied by flow cytometry, allowing evaluation of blast cell positivity as well as their mean fluorescence intensity. These quantitative data were made comparable between centers by means of a calibration curve established with the same reagents in all laboratories. RESULTS: Quantitative expression of class I epitope was significantly higher than that of class II and class III epitopes (p<0.0001). The three classes were more frequently expressed in M0 and M1 and less in M3 and M5. The highest levels of CD34 expression were observed in M2, M0 and M1 and the lowest in M3, M5 and BAL for class II and III. CD34 expression was lower for all classes in cases with a normal karyotype, compared to in cases with structural or numerical abnormalities. INTERPRETATION AND CONCLUSIONS: In cases with a t(9;22) the expression of class I was significantly higher than that of class II and III and the opposite was observed in AML with t(15;17). Moreover, as a whole, a high intensity of class III CD34 appeared to be a marker of good prognosis