The trend of the crude prevalence rates of JAK2 V617F mutation in samples taken during the 7 time periods from the diagnosis to the last follow-up. Time periods: 0 = at diagnosis (n = 70), 1 = from diagnosis to 1 year of follow-up (n = 72), 2 = from more than 1 year to 2 years of follow-up (n = 42), 3 = from more than 2 years to 3 years of follow-up (n = 31), 4 = from more than 3 years to 5 years of follow-up (n = 30), 5 = from more than 5 years to 8 years of follow-up (n = 20), 6 = from more than 8 years to the last follow-up (n = 39). Bars indicate 95% confidence interval.