On the other hand, Usseglio et al. found that CALR mutations could be detected in low allelic burden (< 4%) JAK2V617F-mutated ET suggesting that the frequency of CALR and JAK2V617F co-mutations might be further increased if a highly sensitive test was employed to detect JAK2V617F mutation in CALR-mutated ET [35]. This evidence concerns the gene CALR and essential thrombocythemia.