Characteristics of ET and PV patients at diagnosis. Expression of JAK2-V617F and results of the PRV-1 assay, endogenous erythroid colony (EEC) and endogenous megakaryocytic colony (EMC) assays, and dosage of serum EPO are shown according to the percentage of total JAK2 represented by JAK2-V617F in blood granulocyte cDNAs. Filled rectangles show increased expression of PRV-1 (defined by a PRV-1 CT/ABL CT ratio < 0.850), positive EEC and EMC assays, and low (< 3.3 IU/L) serum EPO; open rectangles, normal PRV-1 expression, negative EEC and EMC assays, and normal or high serum EPO. Empty spaces mean that the assay was not performed.