Higher Sensitivity and Detection of Homozygous/Hemizygous State of JAK2 Mutation Using Plasma.

We recently reported that analysis of plasma rather than peripheral blood cells improves detection of the JAK2 V617F mutation, the most characteristic molecular abnormality in patients with non-chronic myeloid leukemia (CML)-myeloproliferative disease (MPD). To expand on these findings, we tested 634 consecutive paired plasma and cell samples for the V617F mutation and mutations in JAK2 exon 12. All patients were clinically suspected of having a non-CML MPD. Testing was performed using direct bidirectional sequencing. The V617F mutation was detected in the plasma of 151 (24%) patients but in only 140 (22%) paired cell samples. No patients were positive by cell analysis and negative by plasma analysis while 7% of patients positive by plasma were negative by cells. Of the 151 V617F-positive samples, 58 (38%) showed homozygous/hemizygous mutation by plasma analysis; 36 (24%) were homozygous/hemizygous by cell analysis. Upon quantifying the V617F mutant peak relative to wild-type peak, plasma exhibited significantly higher relative mutant JAK2 transcript than cell samples (P<0.001). None of the 634 paired samples had exon 12 mutations, nor did an additional 130 plasma samples from patients with confirmed MPD. However, two novel mutations, C618R and V617I, were identified. These data confirm that plasma is enriched with tumor-specific nucleic acid, allowing more sensitive detection of the JAK2 V617F mutation and homozygous/hemizygous state than cell analysis.