Interlaboratory development and validation of a HRM method applied to the detection of JAK2 exon 12 mutations in polycythemia vera patients

Idiopathic erythrocytosis: a germline disease?

Polycythemia Vera (PV) is typically caused by V617F or exon 12 JAK2 mutations. Little is known about Polycythemia cases where no JAK2 variants can be detected, and no other causes identified. This condition is defined as idiopathic erythrocytosis (IE). We evaluated clinical-laboratory parameters of a cohort of 56 IE patients and we determined their molecular profile at diagnosis with paired blood/buccal-DNA exome-sequencing coupled with a high-depth targeted OncoPanel to identify a possible underling germline or somatic cause. We demonstrated that most of our cohort (40/56: 71.4%) showed no evidence of clonal hematopoiesis, suggesting that IE is, in large part, a germline disorder. We identified 20 low mutation burden somatic variants (Variant allelic fraction, VAF, < 10%) in only 14 (25%) patients, principally involving DNMT3A and TET2. Only 2 patients presented high mutation burden somatic variants, involving DNMT3A, TET2, ASXL1 and WT1. We identified recurrent germline variants in 42 (75%) patients occurring mainly in JAK/STAT, Hypoxia and Iron metabolism pathways, among them: JAK3-V722I and HIF1A-P582S; a high fraction of patients (48.2%) resulted also mutated in homeostatic iron regulatory gene HFE-H63D or C282Y. By generating cellular models, we showed that JAK3-V722I causes activation of the JAK-STAT5 axis and upregulation of EPAS1/HIF2A, while HIF1A-P582S causes suppression of hepcidin mRNA synthesis, suggesting a major role for these variants in the onset of IE.

Revisiting Diagnostic performances of serum erythropoïetin level and JAK2 mutation for polycythemias: analysis of a cohort of 1090 patients with red cell mass measurement

We assessed the diagnostic performances of erythropoietin and JAK2 mutations in 1,090 patients with suspected polycythemia who were referred for red cell mass (RCM) measurement. In patients with a high haematocrit and/or haemoglobin level, a low erythropoietin level (<=3·3 mUI/ml) and JAK2 mutation showed comparable positive predictive value (PPV) for true polycythemia (RCM>=125%), 92·1% and 90% respectively. A very-low erythropoietin level (<=1·99 mUI/ml) had a PPV of 100% for polycythemia vera (PV) diagnosis. We confirmed the correlations between RCM, erythropoietin and JAK2 variant allelic frequency in PV patients. This study prompts the need to revisit the role of EPO in PV diagnostic criteria.

Identification of Variants Associated With Rare Hematological Disorder Erythrocytosis Using Targeted Next-Generation Sequencing Analysis

An erythrocytosis is present when the red blood cell mass is increased, demonstrated as elevated hemoglobin and hematocrit in the laboratory evaluation. Congenital predispositions for erythrocytosis are rare, with germline variants in several genes involved in oxygen sensing (VHL, EGLN1, and EPAS1), signaling for hematopoietic cell maturation (EPOR and EPO), and oxygen transfer (HBB, HBA1, HBA2, and BPGM) that were already associated with the eight congenital types (ECYT1–8). Screening for variants in known congenital erythrocytosis genes with classical sequencing approach gives a correct diagnosis for only up to one-third of the patients. The genetic background of erythrocytosis is more heterogeneous, and additional genes involved in erythropoiesis and iron metabolism could have a putative effect on the development of erythrocytosis. This study aimed to detect variants in patients with yet unexplained erythrocytosis using the next-generation sequencing (NGS) approach, targeting genes associated with erythrocytosis and increased iron uptake and implementing the diagnostics of congenital erythrocytosis in Slovenia. Selected 25 patients with high hemoglobin, high hematocrit, and no acquired causes were screened for variants in the 39 candidate genes. We identified one pathogenic variant in EPAS1 gene and three novel variants with yet unknown significance in genes EPAS1, JAK2, and SH2B3. Interestingly, a high proportion of patients were heterozygous carriers for two variants in HFE gene, otherwise pathogenic for the condition of iron overload. The association between the HFE variants and the development of erythrocytosis is not clearly understood. With a targeted NGS approach, we determined an actual genetic cause for the erythrocytosis in one patient and contributed to better management of the disease for the patient and his family. The effect of variants of unknown significance on the enhanced production of red blood cells needs to be further explored with functional analysis. This study is of great significance for the improvement of diagnosis of Slovenian patients with unexplained erythrocytosis and future research on the etiology of this rare hematological disorder.

Diagnosis and management of non-clonal erythrocytosis remains challenging: a single centre clinical experience

Erythrocytosis has a diverse background. While polycythaemia vera has well defined criteria, the diagnostic approach and management of other types of erythrocytosis are more challenging. The aim of study was to retrospectively analyse the aetiology and management of non-clonal erythrocytosis patients referred to a haematology outpatient clinic in an 8-year period using a 3-step algorithm. The first step was inclusion of patients with Hb > 185 g/L and/or Hct > 0.52 in men and Hb > 165 g/L and/or Hct > 0.48 in women on two visits ≥ two months apart, thus confirming true erythrocytosis. Secondly, polycythaemia vera was excluded and secondary causes of erythrocytosis (SE) identified. Thirdly, idiopathic erythrocytosis patients (IE) were referred to next-generation sequencing for possible genetic background evaluation. Of the 116 patients, 75 (65%) are men and 41 (35%) women, with non-clonal erythrocytosis 34/116 (29%) had SE, 15/116 (13%) IE and 67/116 (58%) stayed incompletely characterized (ICE). Patients with SE were significantly older and had significantly higher Hb and Hct compared to patients with IE. Most frequently, SE was attributed to obstructive sleep apnoea and smoking. Phlebotomies were performed in 56, 53 and 40% of patients in the SE, IE, and ICE group, respectively. Approx. 70% of patients in each group received aspirin. Thrombotic events were registered in 12, 20 and 15% of SE, IE and ICE patients, respectively. Congenital erythrocytosis type 4 (ECYT4) was diagnosed in one patient. The study demonstrates real-life management of non-clonal erythrocytosis which could be optimized using a 3-step diagnostic algorithm.

Kidney Involvement in Patients With Chronic Myelomonocytic Leukemia or BCR-ABL-Negative Myeloproliferative Neoplasms

Introduction

The identification of specific molecular signatures and the development of new targeted drugs have changed the paradigm of onco-nephrology, now allowing a multiscale approach of kidney involvement related to hematologic malignancies relying on combined hematologic and molecular assessments. In this study, we aimed to refine the spectrum of kidney disorders associated with chronic myelomonocytic leukemia (CMML) or BCR-ABL–negative myeloproliferative neoplasms (MPNs), 2 very rare conditions scarcely described.

Methods

Case series. Patients with myeloid neoplasms who were referred to Toulouse University Hospital Nephrology Unit and were diagnosed with acute kidney injury (AKI), chronic kidney disease (CKD), or urine abnormalities were retrospectively included.

Results

Eighteen patients (males n=13, CMML n=8, essential thrombocytosis [ET] n=7, polycythemia vera [PV] n=1, and myelofibrosis n=2) developed kidney disease 7.7±2 years after the diagnosis of the malignancy. Twelve patients had AKI at presentation. Eight patients had glomerular presentation (high-range proteinuria 33%, microscopic hematuria 56%). Kidney biopsy (n=14) showed various patterns, including pauci-immune glomerulosclerosis (n=5), extramedullary hematopoiesis (n=6), or tubular atrophy and interstitial fibrosis with polymorphic inflammation (n=8). Immunostaining of CD61 confirmed the infiltration of megakaryocytes within glomeruli or interstitium in 5 of 8 patients. Other pictures of glomerulopathy were identified in 3 patients (IgA nephropathy n=2, AA amyloidosis n=1). Massive kidney infiltration by CMML was identified in 1 patient. After a mean follow-up of 24±6 months, malignancy was considered as stable in 11 patients (61%), but 22% of patients had progressed to end-stage renal failure. The remaining had persistently reduced kidney function. No correlation between the malignancy and the renal presentation and outcomes could be identified.

Conclusions

Kidney complications of CMML/MPN are heterogenous, and kidney biopsy may help to identify new molecular targets to prevent the development of kidney fibrosis.

Diagnosis of exon 12-positive polycythemia vera rescued by NGS

A JAK2V617F-negative polycythemia associated with low serum epo needs to be tested for an exon 12 JAK2 mutation. When negative, due to potential serious complications in PV, a next generation sequencing is necessary to rule out false negative results.

Interferon Alpha Therapy Increases Pro-Thrombotic Biomarkers in Patients with Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPN) are associated with an increased risk of arterial and venous thrombosis. Pegylated-interferon alpha (IFN) and hydroxyurea (HU) are commonly used to treat MPN, but their effect on hemostasis has not yet been studied. The aim of our study was to determine whether IFN and HU impact the biological hemostatic profile of MPN patients by studying markers of endothelial, platelet, and coagulation activation. A total of 85 patients (50 polycythemia vera and 35 essential thrombocythemia) were included: 28 treated with IFN, 35 with HU, and 22 with no cytoreductive drug (non-treated, NT). Von Willebrand factor, shear-induced platelet aggregation, factor VIII coagulant activity (FVIII:C), fibrinogen, and thrombin generation with and without exogenous thrombomodulin were significantly higher in IFN-treated patients compared to NT patients, while protein S anticoagulant activity was lower. In 10 patients in whom IFN therapy was discontinued, these hemostatic biomarkers returned to the values observed in NT patients, strongly suggesting an impact of IFN therapy on endothelial and coagulation activation. Overall, our study shows that treatment with IFN is associated with significant and reversible effects on the biological hemostatic profile of MPN patients. Whether they could be associated with an increased thrombotic risk remains to be determined in further randomized clinical studies.

Coexistence of JAK2 or CALR mutation is a rare but clinically important event in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors

INTRODUCTION

There are 7 designated conditions under the category of myeloproliferative neoplasms (MPN), including chronic myelogenous leukemia (CML) and classical MPN, that is, polycythemia vera (PV), essential thrombocythaemia (ET), and primary myelofibrosis (PMF). Recently, reports about Philadelphia and JAK2 V617F-positive MPN cases have been described in literature. The coexistence of different molecular defects may change the clinical and laboratory manifestation of MPN and may result in an inappropriate interpretation of the response to treatment with tyrosine kinase inhibitors in CML patients.

METHODS

The morphological, cytogenetic, and molecular genetic data from a retrospective analysis of 592 adult patients aged 18-86 years diagnosed with CML were analyzed.

RESULTS

In 5 CML patients, the presence of JAK2 V617F or CALR mutation was confirmed. Three of 4 TKI-treated patients did not reach complete hematologic response due to the persistence of thrombocytosis and/or splenomegaly. In all of them (in 3 with JAK2 V617F mutation and 1 with CALR mutation), thrombocytosis was present at the time when complete cytogenetic response was documented. In 3 out of 4 reported CML patients, thrombocytosis and/or splenomegaly were still present even at the time when deep molecular response was reached.

CONCLUSION

In our opinion, a detailed evaluation and appropriate interpretation of clinical and laboratory data in such a category of patients seem to be extremely important, especially when a decision about the TKI change due to therapy failure is considered.

Validating the Sensitivity of High-Resolution Melting Analysis for JAK2 V617F Mutation in the Clinical Setting

BACKGROUND

Janus kinase 2 (JAK2) plays an important role in normal hematopoietic growth factor signaling. The detection of the JAK2 V617F mutation (c.1849GNT, GTC → TTC) is crucial for the diagnosis of myeloproliferative neoplasm (MPN) and has become the essential criteria for diagnosis of MPN by the WHO. High-resolution melt (HRM) curve analysis is a nongel-based, closed-tube method, in which PCR amplification and subsequent analysis are sequentially performed in the well, making it more convenient than other scanning methodologies.

METHODS

We evaluated JAK2 V617F mutation by HRM. Twenty-nine patients diagnosed with MPN were examined. We studied the analytical sensitivity of the HRM analysis using real-time polymerase chain reaction (PCR) for identifying the JAK2 V617F mutation. Additionally, the sensitivity of HRM analysis and allele-specific PCR (AS-PCR) assay was compared.

RESULTS

The JAK2 V617F mutation was successfully discriminated at an abundance of 6% or above in HRM analysis. Both HRM analysis and AS-PCR showed 100% accuracy with detection limits of 6% and 2.5%, respectively.

CONCLUSION

HRM analysis is a fast, simple, reliable, and nonexpensive method for the detection of the JAK2 V617F mutation. However, more validation of the detection limits of HRM analysis should be performed before declaration of the analytic sensitivity of the method.

Laboratory Investigation of Myeloproliferative Neoplasms (MPNs): Recommendations of the Canadian Mpn Group

OBJECTIVES

To standardize diagnostic investigations for myeloproliferative neoplasms (MPNs) to increase homogeneity in patient care and to streamline diagnostic approaches in the most efficient and cost-effective manner.

METHODS

The development of Canadian expert consensus recommendations for the diagnosis of MPNs began with a review of the following: clinical evidence, daily practice, existing treatment guidelines, and availability of diagnostic tools. Each group member was assigned a specific topic, which they discussed with the entire group during several consensus meetings.

RESULTS

This document provides the Canadian MPN group's recommendations, proposed diagnostic algorithms, and background evidence upon which decisions were made.

CONCLUSIONS

Standardization of diagnostic investigations will increase homogeneity in patient care and provide a foundation for future clinical research in this rapidly evolving therapeutic area. Streamlining diagnostic approaches in the most efficient and cost-effective manner will also result in significant cost saving for the health care system.

Detection of JAK2 Exon 12 Mutations in JAK2 V617F-Negative Polycythemia Vera Patients by Cloning Technique

INTRODUCTION

The identification of mutations of the JAK2 gene is a useful marker in the diagnosis of polycythemia vera (PV) patients. We studied the frequency of JAK2 mutations in a group of PV patients because data are still very limited regarding this subject in Polish patients.

METHODS

The JAK2 V617F mutation was examined using the amplification refractory mutation system (ARMS)-PCR method. Direct sequencing and a cloning technique were performed to determine alternations in exon 12 of the JAK2 gene.

RESULTS

A group of 90 consecutive patients with a suspected diagnosis of polycythemia vera were investigated. In 91% of the cases, the JAK2 V617F mutation was identified. The remaining JAK2 V617F-negative patients were subjected to examination for JAK2 exon 12 by direct PCR product sequencing and the cloning technique. The following mutations were identified: H538-K539delinsL, E543-D544del and N542-E543del. These exon 12 mutants constituted 50% of PV JAK2 V617F-negative group and 4.4% (out of 90) of all PV patients (JAK2 V617F-positive and JAK2 V617F-negative).

CONCLUSION

Our results demonstrate the prevalence of JAK2 mutations (V617F and in exon 12) in PV cases. Moreover, the data show that direct sequencing is not an adequate technique for exon 12 mutation identification; therefore, appropriate methodology should be considered for using this molecular marker in the process of diagnosis.

The JAK2 V617F mutational status and allele burden may be related with the risk of venous thromboembolic events in patients with Philadelphia-negative myeloproliferative neoplasms

INTRODUCTION

Patients with Philadelphia-negative myeloproliferative neoplasms (Ph(-) MPNs) are at increased risk of thromboembolic and hemorrhagic complications. The aim of the study was to determine the relationship between JAK2 V617F mutational status, JAK2 V617F allele burden and the risk of vascular complications occurrence.

MATERIALS AND METHODS

Analysis was performed in a cohort of 186 patients diagnosed with polycythemia vera (53), essential thrombocythemia (114), primary myelofibrosis (11), and unclassified MPN (8). The risk of vascular complications development was analyzed in 126 JAK2 V617F-positive patients with respect to allele burden assessed with allele-specific 'real-time' quantitative polymerase chain reaction (AS RQ-PCR).

RESULTS

Overall prevalence of any vascular complications was 44.6%. Arterial thrombosis occurred in 20.4%, venous thromboembolism (VTE) in 11.3%, bleeding episodes in 24.7% of patients. Individuals harboring JAK2 V617F mutation, regardless of MPN type, were at higher risk of VTE (OR=5.15, 95%CI: 1.16-22.90, P=0.024), mainly deep vein thrombosis (DVT). JAK2 allele burden higher than 20% identified patients with 7.4-fold increased risk of VTE (95%CI: 1.6-33.7, P=0.004), but not of arterial thrombosis, neither of bleeding complications, and remained the only significant VTE risk factor in multivariate logistic regression. High allele burdens (over 50%) were strikingly associated with proximal DVT cases, but not with distal DVT.

CONCLUSIONS

The group of MPN patients with JAK2 V617F allele burden higher than 20% may benefit the most from vigilant monitoring and appropriate prophylaxis against vascular events. Inclusion of JAK2 V617F mutant allele burden in new risk stratifications seems to be justified and requires controlled prospective trials.

Frequency and molecular characteristics of calreticulin gene (CALR) mutations in patients with JAK2 -negative myeloproliferative neoplasms

In 2013, Nangalia et al. and Klampfl et al. found a recurrent and abundant mutation in the calreticulin gene (CALR), mutually exclusive with JAK2 and MPL alterations. At present, the data concerning the new mutation, i.e. its prevalence, allele burden and clinical significance, are scarce. We report the incidence and molecular characteristics of CALR mutations in a group of 184 Polish patients with myeloproliferative neoplasms (MPNs). Clinical data analysis revealed significant differences between JAK2 V617F-mutated and CALR-mutated groups. In essential thrombocythemia patients, hemoglobin levels and leukocyte counts were significantly higher in JAK2-positive than in CALR-positive patients (p = 0.023 and p = 0.017, respectively), but the CALR-positive patients had significantly higher platelet counts (p = 0.022). Patients harboring CALR mutations were also younger at the time of diagnosis (p = 0.039). In primary myelofibrosis patients, the degree of anemia was less severe in those who were CALR exon 9 mutation-positive than in those who were JAK2 V617F-positive (p = 0.048).

How I treat polycythemia vera

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm associated with JAK2 mutations (V617F or exon 12) in almost all cases. The World Health Organization has defined the criteria for diagnosis, but it is still unclear which parameter (hemoglobin or hematocrit) is the most reliable for demonstrating increased red cell volume and for monitoring response to therapy; also, the role of bone marrow biopsy is being revisited. PV is associated with reduced survival because of cardiovascular complications and progression to post-PV myelofibrosis or leukemia. Criteria for risk-adapted treatment rely on the likelihood of thrombosis. Controlled trials have demonstrated that incidence of cardiovascular events is reduced by sustained control of hematocrit with phlebotomies (low-risk patients) and/or cytotoxic agents (high-risk patients) and antiplatelet therapy with aspirin. Hydroxyurea and interferon may be used as first-line treatments, whereas busulfan is reserved for patients that are refractory or resistant to first-line agents. However, there is no evidence that therapy improves survival, and the significance of reduction of JAK2 mutated allele burden produced by interferon is unknown. PV is also associated with a plethora of symptoms that are poorly controlled by conventional therapy. This article summarizes my approach to the management of PV in daily clinical practice.

Quantitative threefold allele-specific PCR (QuanTAS-PCR) for highly sensitive JAK2 V617F mutant allele detection

Background

The JAK2 V617F mutation is the most frequent somatic change in myeloproliferative neoplasms, making it an important tumour-specific marker for diagnostic purposes and for the detection of minimal residual disease. Sensitive quantitative assays are required for both applications, particularly for the monitoring of minimal residual disease, which requires not only high sensitivity but also very high specificity.

Methods

We developed a highly sensitive probe-free quantitative mutant-allele detection method, Quantitative Threefold Allele-Specific PCR (QuanTAS-PCR), that is performed in a closed-tube system, thus eliminating the manipulation of PCR products. QuantTAS-PCR uses a threefold approach to ensure allele-specific amplification of the mutant sequence: (i) a mutant allele-specific primer, (ii) a 3′dideoxy blocker to suppress false-positive amplification from the wild-type template and (iii) a PCR specificity enhancer, also to suppress false-positive amplification from the wild-type template. Mutant alleles were quantified relative to exon 9 of JAK2.

Results

We showed that the addition of the 3′dideoxy blocker suppressed but did not eliminate false-positive amplification from the wild-type template. However, the addition of the PCR specificity enhancer near eliminated false-positive amplification from the wild-type allele. Further discrimination between true and false positives was enabled by using the quantification cycle (Cq) value of a single mutant template as a cut-off point, thus enabling robust distinction between true and false positives. As 10,000 JAK2 templates were used per replicate, the assay had a sensitivity of 1/10^-4 per replicate. Greater sensitivity could be reached by increasing the number of replicates analysed. Variation in replicates when low mutant-allele templates were present necessitated the use of a statistics-based approach to estimate the load of mutant JAK2 copies. QuanTAS-PCR showed comparable quantitative results when validated against a commercial assay.

Conclusions

QuanTAS-PCR is a simple, cost-efficient, closed-tube method for JAK2 V617F mutation quantification that can detect very low levels of the mutant allele, thus enabling analysis of minimal residual disease. The approach can be extended to the detection of other recurrent single nucleotide somatic changes in cancer.

Methods for detecting mutations in the human JAK2 gene

Mutations in the JAK2 gene are prevalent in the human myeloid malignancies, being present in virtually all cases of polycythemia vera, and a significant proportion of patients with other myeloproliferative disorders. Various methods for the detection of acquired mutations in this gene are available depending on the need for sensitivity, quantification, or the ability to detect many different mutations. We summarize the various methods published and discuss their relative merits for each application. Two commonly used methods, quantitative real-time PCR (QPCR) for the detection of the JAK2 V617F mutation and high resolution melt-curve analysis (HRM) for the detection of multiple mutations within JAK2 exon 12, demonstrate the utility of each method and their limitations. The choice of methodology is dependent on the application; therefore there is no gold standard for detecting mutations in this gene.

BCR-ABL1-negative chronic myeloid neoplasms: an update on management techniques

Recent discoveries concerning mutations associated with chronic myeloproliferative neoplasms have modified our understanding of the biology of these incurable diseases and guided us to the development of inhibitors active on the constitutively activated JAK-STAT pathway. Concurrently, numerous studies dealt with clinical issues; it led to a revised WHO classification; clarified the role of mutated JAK2 and leukocytosis in the pathogenesis of cardiovascular events; allowed the development of risk prognostic scores and tools for monitoring response to therapy; and resulted in completion of Phase III trials with JAK2 inhibitor in myelofibrosis. All these results hold the promise of improving patient prognostication and therapeutic approach, with the aim of efficiently preventing disease-associated complications and, hopefully, to improve the dismal survival associated with myelofibrosis. This review discusses how to manage, according to current clinical practice, the steps of diagnosis, prognostication and therapeutic choices in myeloproliferative neoplasm patients.

Novel strategy to evaluate infectious salmon anemia virus variants by high resolution melting

Genetic variability is a key problem in the prevention and therapy of RNA-based virus infections. Infectious Salmon Anemia virus (ISAv) is an RNA virus which aggressively attacks salmon producing farms worldwide and in particular in Chile. Just as with most of the Orthomyxovirus, ISAv displays high variability in its genome which is reflected by a wider infection potential, thus hampering management and prevention of the disease. Although a number of widely validated detection procedures exist, in this case there is a need of a more complex approach to the characterization of virus variability. We have adapted a procedure of High Resolution Melting (HRM) as a fine-tuning technique to fully differentiate viral variants detected in Chile and projected to other infective variants reported elsewhere. Out of the eight viral coding segments, the technique was adapted using natural Chilean variants for two of them, namely segments 5 and 6, recognized as virulence-associated factors. Our work demonstrates the versatility of the technique as well as its superior resolution capacity compared with standard techniques currently in use as key diagnostic tools.

The JAK2 exon 12 mutations: a comprehensive review

A variety of acquired mutations targeting JAK2 exon 12 are present in those patients with the myeloproliferative neoplasm, polycythemia vera, that lack the more common JAK2V617F mutation. Both mutation types perturb erythropoiesis, with individuals presenting with a raised hematocrit, reduced serum erythropoietin levels, and erythropoietin-independent erythroid progenitor cells. However, there are also phenotypic differences that, until recently, precluded a significant proportion of patients with a JAK2 exon 12 mutation from receiving an appropriate diagnosis. Here, we review the literature published on the JAK2 exon 12 mutations and compare the biology associated with these mutations with that of JAK2V617F.

Nested high-resolution melting curve analysis a highly sensitive, reliable, and simple method for detection of JAK2 exon 12 mutations--clinical relevance in the monitoring of polycythemia

JAK2 exon 12 mutations are found in myeloproliferative disorders characterized by erythrocytosis. Lying in a 33-bp region and conserving the open reading frame, they often present a low allelic burden (<10%), which excludes screening with techniques such as allele-specific PCR or different sequencing protocols. High-resolution melting (HRM), a fast in-tube method, seems the most accurate routine technique for that. We describe a reliable and powerful nested HRM technique, independent of DNA preparation and with technical sensitivity of 100% (95% CI, 93% to 100%) and specificity of 96.7% (95% CI, 89.7% to 96.7%). Screening a cohort of 10 idiopathic erythrocytosis, 28 polycythemia vera, and 7 secondary erythrocytosis cases allowed the detection of 15 mutants, including 9 different mutations, of which 3 were unreported, all in the polycythemia vera group, and presented a characteristic profile: pure erythrocytosis associated with low serum erythropoietin. Threshold detection level ranged from 1% to 3% allelic burden, depending on the mutation. All of the HRM positive signals were found mutated by sequencing. Six of them (40%), however, required cloning before sequencing, because of low allelic burden. Classic techniques such as genomic sequencing may therefore miss patients with mutations. Given its sensitivity, HRM (and nested HRM) can be used in routine diagnosis and seems to be the most efficient of current techniques for detection of JAK2 exon 12 mutations.

Molecular and clinical features of the myeloproliferative neoplasm associated with JAK2 exon 12 mutations

Although approximately 95% of patients with polycythemia vera (PV) harbor the V617F mutation in JAK2 exon 14, several mutations in exon 12 have been described in the remaining patients. We conducted a European collaborative study to define the molecular and clinical features of patients harboring these mutations. Overall, 106 PVs were recruited and 17 different mutations identified. Irrespective of the mutation, two-thirds of patients had isolated erythrocytosis, whereas the remaining subjects had erythrocytosis plus leukocytosis and/or thrombocytosis. Compared with JAK2 (V617F)-positive PV patients, those with exon 12 mutations had significantly higher hemoglobin level and lower platelet and leukocyte counts at diagnosis but similar incidences of thrombosis, myelofibrosis, leukemia, and death. In a multivariable analysis, age more than 60 years and prior thrombosis predicted thrombosis. These findings suggest that, despite the phenotypical difference, the outcome of JAK2 exon 12 mutations-positive PV is similar to that of JAK2 (V617F)-positive PV.

Is high resolution melting analysis (HRMA) accurate for detection of human disease-associated mutations? A meta analysis

BACKGROUND

High Resolution Melting Analysis (HRMA) is becoming the preferred method for mutation detection. However, its accuracy in the individual clinical diagnostic setting is variable. To assess the diagnostic accuracy of HRMA for human mutations in comparison to DNA sequencing in different routine clinical settings, we have conducted a meta-analysis of published reports.

METHODOLOGY/PRINCIPAL FINDINGS

Out of 195 publications obtained from the initial search criteria, thirty-four studies assessing the accuracy of HRMA were included in the meta-analysis. We found that HRMA was a highly sensitive test for detecting disease-associated mutations in humans. Overall, the summary sensitivity was 97.5% (95% confidence interval (CI): 96.8-98.5; I(2) = 27.0%). Subgroup analysis showed even higher sensitivity for non-HR-1 instruments (sensitivity 98.7% (95%CI: 97.7-99.3; I(2) = 0.0%)) and an eligible sample size subgroup (sensitivity 99.3% (95%CI: 98.1-99.8; I(2) = 0.0%)). HRMA specificity showed considerable heterogeneity between studies. Sensitivity of the techniques was influenced by sample size and instrument type but by not sample source or dye type.

CONCLUSIONS/SIGNIFICANCE

These findings show that HRMA is a highly sensitive, simple and low-cost test to detect human disease-associated mutations, especially for samples with mutations of low incidence. The burden on DNA sequencing could be significantly reduced by the implementation of HRMA, but it should be recognized that its sensitivity varies according to the number of samples with/without mutations, and positive results require DNA sequencing for confirmation.

Rapid detection of JAK2 V617F mutation using high-resolution melting analysis with LightScanner platform

BACKGROUND

Detection of the JAK2 mutation has recently been included under the essential diagnostic criteria for myeloproliferative neoplasm (MPN). High-resolution melt (HRM) curve analysis, a nongel-based, automated system, is introduced as a means of mutation scanning without the requirement of any post-PCR handling.

METHODS

We studied the sensitivity and reproducibility of LightScanner™ platform in the detection of JAK2 V617F mutation and the availability for diagnostic use in MPN.

RESULTS

The reproducible sensitivity of HRM analysis with LightScanner™ platform was 5% for the detection of JAK2 V617F mutation. In the test of blind screening of 105 samples (48 Ph- MPN and 57 Ph+ chronic myeloid leukemia), the identical judgement was interpreted by two blinded investigators. HRM analysis of all cases was fully concordant with the results of PCR-RFLP and direct sequencing.

CONCLUSIONS

The HRM method developed here is an extremely sensitive, accurate and reliable technique and allows high-throughput, fast pre-screening to select for sequencing only those specimens that most likely contain mutant JAK2 V617F allele(s).