JAK2 and myeloproliferative disorder: On comparison of JAK2V617F positive and negative MPN, the Breslow–Day test identified two SNPs that had stronger effects in JAK2V617F-positive cases: rs12339666 (Breslow–Day P=2.8 × 10−18), which tags the JAK2 46/1 haplotype, and rs2736100 (TERT; Breslow–Day P=0.0026).