As shown in Fig 1, untreated PV patients had significantly higher IGF-1R (361.5, 227.8–461.1) than did secondary polycythemia patients (58.13, 15.46–90.43), normal controls (49.20, 14.63–113.5), and treated PV patients (52.29, 23.89–149.3) (P<0.05). Here, IGF1R is linked to acquired polycythemia vera.