Since mutations in JAK2, such as JAK2 V617F, on chromosome 9p are known to cause polycythemia vera, we performed a multiple regression of age at time of blood draw, sex, and PACER score to predict erythrocyte counts for 11 individuals with CN-LOH or loss of chromosome 9p and erythrocyte count. Here, JAK2 is linked to acquired polycythemia vera.