A positive EPO-JAKPOT score had a Sn of 0.95 (95% CI, 0.83–0.98), Sp of 0.66 (95% CI, 0.58–0.72), −LR of 0.07 (95% CI, 0.02–0.30), and +LR of 2.7 (95% CI, 2.2–3.4) to diagnose JAK2 mutant erythrocytosis (Table 2, and Supplemental Materials Table S3). Here, EPO is linked to polycythemia.