A positive JAKPOT score (Figure 2) had a Sn of 0.88 (95% CI, 0.73–0.94), Sp of 0.65 (95% CI, 0.57–0.72), −LR of 0.19 (95% CI, 0.08–0.44), and +LR 2.5 (95% CI, 2.0–3.2) for the diagnosis of JAK2 mutant erythrocytosis (Table 2, and Supplementary Materials Table S2). The gene discussed is JAK2; the disease is polycythemia.