Abstract Detection of the JAK2 V617F somatic mutation has become standard care for diagnosing myeloproliferative neoplasms (MPN), including polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). However, quantitation of V617F mutation allele burden (MAB) is not routinely evaluated, and the V617F MAB data are less frequently reported in the United States MPN population. We studied the correlation between V617F MAB and hematologic characteristics in our South Texas MPN patient population using a clinically validated allelic discrimination quantitative PCR (AD-qPCR) assay. DNA was extracted from blood or bone marrow (BM) samples using the EZ1 DNA Blood Kit (Qiagen). AD-qPCR was performed on the ABI Prism 7900HT Sequence Detection System using TaqMan MGB probes (Applied Biosystems). The quantity of V617F MAB was determined by the comparative CT method (ΔΔCt method). The type of MPN, complete blood count (CBC) data, and clinical status were correlated with the V617F MAB. CBC data were collected on or near the date of JAK2 V617F MAB testing. Correlation and means comparison between V617F MAB and clinical data were analyzed by the Pearson correlation coefficient and t - Test, respectively. Of 638 blood and BM samples tested for V617F MAB due to clinical suspicion of MPN, 43 patients with detectable V617F allele and available hematologic data were included in this study. Fifteen of 43 patients had more than one specimen tested for the V617F MAB. For each of these 15 patients, only one representative V617F MAB result was included in this study. Among 43 MPN patients, 21 were diagnosed as PV, 18 ET, 4 myelofibrosis (3 PMF and 1 PV that progressed to fibrotic stage). Overall, the mean V617F MAB is higher in PV patients than ET patients (37.5% versus 19.2%). The mean V617F MAB of the 4 myelofibrosis patients is 55.2%. In PV patients, V617F MAB is positively correlated to hematocrit (HCT) level (R=0.72, P 50%. Compared to patients with lower V617F MAB ( 50%) have significantly higher HCT, RBC, HGB, and WBC (Table 1) count. In ET patients, V617F MAB is positively correlated to RBC (R=0.61, P 20%) versus those with lower V617F MAB ( Our study indicates that in PV patients, the V617F MAB was positively correlated with HCT, RBC, HGB as well as WBC, and a MAB greater than 50% reflected a more severe disease status. For ET and PMF, a larger scale study is needed to draw meaningful conclusions. Our data from a South Texas MPN population supports that JAK2 V617F MAB may provide meaningful insight into the clinical status of PV patients. Download : Download high-res image (181KB) Download : Download full-size image Disclosures No relevant conflicts of interest to declare.