Red cell mass measurement in patients with clinically suspected diagnosis of polycythemia vera or essential thrombocythemia

Role of red cell mass evaluation in myeloproliferative neoplasms with splanchnic vein thrombosis and normal hemoglobin value: a study of the France Intergroupe des Syndromes myeloprolifératifs

Not available.

Erythrocytosis: Diagnosis and investigation

An absolute erythrocytosis is present when the red cell mass is greater than 125% of the predicted. This is suspected when the hemoglobin or hematocrit is above the normal range. An erythrocytosis can be classified as primary or secondary and congenital or acquired. The commonest primary acquired disorder is polycythemia vera. The diagnostic criteria for PV have evolved over time and this is the main diagnosis managed in hematology clinics. There are a variety of rare congenital causes both primary and secondary. In particular in young patients and/or those with a family history a congenital cause is suspected. There remains a larger cohort with acquired erythrocytosis mainly with non-hematological pathology. In order to explore for a cause of erythrocytosis, measurement of the erythropoietin level is a first step. A low erythropoietin level indicates a primary cause and a normal or elevated level indicates a secondary etiology. Further investigation is then dictated by initial findings and includes mutational testing with PCR and NGS for those in whom a congenital cause is suspected. Following this possibly bone marrow biopsy, scans, and further investigation as indicated by history and initial findings. Investigation is directed toward the identification of those with a hematological disorder which would be best managed following guidelines in hematology clinics and referral elsewhere in those for whom there are non-hematological reasons for the elevated hemoglobin.

Polycythemia vera disease profile in an African population-experience from a tertiary facility in Ghana

Objectives

The study describes the clinical and laboratory profile of the patients with polycythemia vera at Komfo Anokye Teaching Hospital in Kumasi, Ghana.

Methods and design

This was a retrospective hospital-based cohort study conducted from September 2020 to August 2022. Hematology clinic entry book was used to identify the patient's unique hospital code. Using these unique codes, retrospective data were collected using an Excel spreadsheet from the Hospital Lightwave health information management system (LHIMS) database.

Results

A total of 20 participants were recruited over the period of 2 years. The overall mean age was 51.53 ± 16.39 years. The hematological profile of the male participants revealed a mean hemoglobin of 18.25 ± 1.373 g/dl, mean hematocrit of 52 ± 3.47%, and a mean platelet of 345.5 ± 180.82. Comparatively, the mean hemoglobin, hematocrit, and platelet for the female participants were higher with figures of 19.26 ± 1.43 g/dl, 53 ± 3.61%, and 816 ± 935.32, respectively. Headache, tiredness, numbness, splenomegaly, and abnormal labs were the most common reasons why participants sought medical attention. Majority (60%) of the study participants had Janus Kinase 2 mutation. New-onset hypertension was identified in 45% of the study participants during follow-up. Thromboembolism was seen in 10% of the study population.

Conclusion

Polycythemia vera is an uncommon disease in Ghana mostly found in older males above 50 years. It is important to recognize it early to initiate therapy aimed at preventing common complications such as hypertension and thromboembolism. Polycythemia vera should be considered a differential diagnosis for patients with secondary hypertension.

Splanchnic Vein Thrombosis in Myeloproliferative Neoplasms: Treatment Considerations and Unmet Needs

Patients who develop splanchnic vein thrombosis (SVT) in the setting of a myeloproliferative neoplasm (MPN) are at risk for complications including portal hypertension, bleeding, thrombosis, and death. Prompt multidisciplinary treatment is thus necessary to prevent long-term sequelae. However, optimal management strategies are not well established due to a paucity of data. In this review, we very briefly discuss the epidemiology, pathophysiology, and prognosis of MPN-SVT and then more comprehensively explore treatment considerations of MPN-SVT, including anticoagulation, endovascular/surgical intervention, and cytoreductive therapy. We will also highlight current gaps in our knowledge of MPN-SVT and conclude by suggesting future directions to optimize the treatment of MPN-SVT and improve outcomes.

Use of nailfold video capillaroscopy in polycythemia vera

Objectives

In this study, we aimed to investigate capillary vessel diameters and structural changes of capillaries by using nailfold video capillaroscopy (NVC) in patients with polycythemia vera (PV).

Patients and methods

This cross-sectional study included a total of 24 patients (19 males, 5 females; mean age: 59.8±12.9 years; range, 50.2 to 68 years) who were diagnosed with PV and 15 healthy controls (11 males, 4 females; mean age: 40.7±5.1 years; range, 36 to 44 years) between June 2016 and February 2017. Nailfold video capillaroscopy was performed by an experienced rheumatologist who was blinded to clinical data. The apical, arterial, and venous limb diameters of capillaries were measured and microvascular changes of capillaries were scored.

Results

When capillaries were evaluated in terms of morphological structures, giant capillary was detected in 67% of the patients with PV and 0% in the control group (p<0.05). The arterial, venous, and apical diameters of the capillaries were significantly higher in the patients with PV compared to the control group (p<0.001).

Conclusion

The presence of giant capillaries and the marked increase of arterial, venous, and apical diameters of capillaries seem to be related to PV. As it additionally plays an important role in diagnosis, prognosis, and treatment monitoring of certain diseases, capillaroscopy can be considered to be a promising microcirculation biomarker.

Recent Advances in the Use of Molecular Analyses to Inform the Diagnosis and Prognosis of Patients with Polycythaemia Vera

Genetic studies in the past decade have improved our understanding of the molecular basis of the BCR-ABL1-negative myeloproliferative neoplasm (MPN) polycythaemia vera (PV). Such breakthroughs include the discovery of the JAK2V617F driver mutation in approximately 95% of patients with PV, as well as some very rare cases of familial hereditary MPN caused by inherited germline mutations. Patients with PV often progress to fibrosis or acute myeloid leukaemia, both associated with very poor clinical outcome. Moreover, thrombosis and major bleeding are the principal causes of morbidity and mortality. As a result of increasingly available and economical next-generation sequencing technologies, mutational studies have revealed the prognostic relevance of a few somatic mutations in terms of thrombotic risk and risk of transformation, helping to improve the risk stratification of patients with PV. Finally, knowledge of the molecular basis of PV has helped identify targets for directed therapy. The constitutive activation of the tyrosine kinase JAK2 is targeted by ruxolitinib, a JAK1/JAK2 tyrosine kinase inhibitor for PV patients who are resistant or intolerant to cytoreductive treatment with hydroxyurea. Other molecular mechanisms have also been revealed, and numerous agents are in various stages of development. Here, we will provide an update of the recent published literature on how molecular testing can improve the diagnosis and prognosis of patients with PV and present recent advances that may have prognostic value in the near future.

Recent advances in prognostication and treatment of polycythemia vera

Polycythemia vera (PV) is a BCR-ABL–negative myeloproliferative neoplasm marked by acquisition of an activating mutation of JAK2, which leads to not only erythrocytosis but also frequently to leukocytosis and thrombocytosis, and is associated with a high symptom burden and increased thrombotic risk. PV has the potential to progress to myelofibrosis or an aggressive form of acute myeloid leukemia. Mutational profiling of patients with PV has led to the development of risk stratification tools to determine an individual’s risk of developing progressive disease. Although the current goals of PV treatment are to alleviate symptoms and reduce thrombotic risk, there are growing efforts to identify disease-modifying agents which will also prevent progression of disease. Here, we give an overview of the developing prognostic tools and therapeutic landscape for PV, focusing on four drug classes: pegylated interferon-alpha 2, MDM2 antagonists, hepcidin mimetics, and histone deacetylase inhibitors.

Polycythaemia vera: molecular genetics, diagnostics and therapeutics

Polycythaemia vera is one of several classical myeloproliferative neoplasms that may occur in a juvenile onset or late-onset adult forms. It is linked to specific genetic mutations that cause a deleterious elevation in the patient's red cell mass. The discourse on genetics includes an exposé on the molecular biology of the disease and how a shared JAK2 V617F mutation can co-exist among three distinct neoplasms. Concepts of genetics and immunology help define the origin and behaviour of the disease: the tracking of allele burdens of mutations (genetic dosage), the timing or order of acquired mutations, the import of bystander mutations and the onco-inflammatory response; all theories are invoked to explain the progression of disease severity and potential transformational leukaemia. The World Health Organization's diagnostic criteria are accessed to focus on the subtleties of the Hb laboratories and sifting through the challenging listing of differential diagnoses that mimic PV, and our report includes an overview of manual and automated phlebotomy (erythrocytapheresis) procedures, enumerating their clinical indications, significance of temporary phlebotomy resistance and optimizing safety/ efficacy, quality and cost. Stratification of low and high-risk disease distinguishes when to commence chemo-cytoreductive therapy in the high-risk patient to prevent thrombotic complications. Drug resistance is circumvented by artfully switching drugs or using novel drug designs.

Development and validation of a sequential two-step algorithm for the screening of individuals with potential polycythaemia vera

In 2016, the WHO included haemoglobin values within normal ranges as a diagnostic criterion for Polycythaemia Vera (PV). Since then, concerns have arisen that a large number of patients are undergoing unnecessary screening for PV. To address this issue, we estimated the prevalence of JAK2 p.V617F in individuals with elevated haemoglobin or haematocrit and developed and validated a screening algorithm for PV. A total of 15,366 blood counts performed in seven non-consecutive days were reviewed, of which 1001 were selected for subsequent JAK2 p.V617F mutation screening. Eight (0.8%) new JAK2 p.V617F-mutated cases were detected. From ROC curves, a two-step algorithm was developed based on the optimal cut-off for the detection of the JAK2 p.V617F mutation. The algorithm was prospectively validated in an independent cohort of 15,298 blood counts. A total of 1595 (10.4%) cases met the criterion for haemoglobin or haematocrit, of whom 581 passed to step 2 (3.8% of the total). The JAK2 p.V617F mutation was detected in 7 of the 501 patients tested, which accounts for 0.04% of the total cohort and 0.4% of patients with erythrocytosis. In conclusion, this data show that our two-step algorithm improves the selection of candidates for JAK2 p.V617F testing.

Polycythemia Vera Presenting With Normal Hemoglobin and Hematocrit: A Rare Variant

Polycythemia vera (PV) is a myeloproliferative neoplasm, and its diagnosis requires elevated hemoglobin level (>16.5 mg/dL in men and >16 mg/dL in women), bone marrow characteristics of PV (hypercellularity for age with trilineage growth), and presence of JAK2 (Janus kinase 2) mutations or subnormal erythropoietin level if JAK2 mutation is not present. There exists a subset of patients with normal hemoglobin and hematocrit due to either from dilution of the blood or from coincidental blood loss anemia but these patients still might have underlying PV. These patients have masked PV, which is a variant of overt PV. We present a case of masked PV presenting with venous thrombosis as a first presentation and with normal blood counts. A 42-year-old male with past medical history of portal vein thrombosis and portal hypertension presented with nausea and vomiting presumably secondary to viral gastroenteritis. He was not an alcoholic nor a smoker. He was diagnosed with portal vein thrombosis six years ago which was treated with warfarin but was never investigated for a cause. His physical exam was within normal limits except he had splenomegaly. His laboratory values on admission showed hemoglobin of 14.1 g/dL, white blood count of 7.4 x109/L, and platelet count of 164 x109/L. His liver function test and renal function tests were within normal limits. His viral gastroenteritis improved within 48 hours. Extensive workup to rule out myeloproliferative neoplasm, thrombophilia, antiphospholipid syndrome, and paroxysmal nocturnal hemoglobinuria was arranged. Final results revealed JAK2V617F genetic mutation with a subsequent bone marrow analysis revealing a hypercellular marrow with increased trilineage hematopoiesis, consistent with primary PV. It is rare for myeloproliferative neoplasms to present with normal blood counts. There is a subgroup of patients with JAK2-positive PV presenting with normal hemoglobin and hematocrit. The prognosis of these subgroups seems to be poor especially when present in the older age group and with associated leukocytosis. Our case emphasizes two important points: first, need for extensive workup in a patient with unusual site thrombosis including JAK2 analysis and second, investigating for myeloproliferative neoplasm if presented with thrombosis even with normal blood counts.

Impact of World Health Organization (WHO) Revised Criteria-2016 on the Diagnosis of Polycythemia Vera

The diagnosis of polycythemia vera (PV) requires the integration of clinical and laboratory findings, bone marrow morphologic features, and JAK2 analysis. JAK2V617F (exon 14) mutation is found in 95% of PV cases. In PV, addition of characteristic bone marrow morphology as one of three major diagnostic criteria allowed reduced hemoglobin/hematocrit threshold for diagnosis to 16.5 g/dL/49% in men and 16 g/dL/48% in women. JAK2 mutation is still the third major diagnostic criterion in PV. Low serum erythropoietin level is now considered as minor criterion in PV and is used to detect cases, which are negative for JAK2 mutation. In this retrospective study, cases diagnosed as PV from January 2013 to December 2015 were reclassified using WHO 2016 criteria. Their clinical and laboratory parameters along with treatment and outcome were studied. Out of 26 patients of previously diagnosed PV, either definitively or provisionally, twenty-one were found to comply with the new 2016 revision of the WHO Criteria. Median age was 55.5 years, with a male preponderance. The median values of hemoglobin, hematocrit and platelets were 17.5 gm/dL, 56.7% and 493 × 10⁹/L, respectively. JAK2V617F was mutated in 17 cases. Bone marrow showed hypercellularity, panmyelosis and marked megakaryocyte dyspoiesis in all patients. All patients had normal oxygen saturation, confirming the primary nature of the disease. Our study, first of its kind in India, underscores the importance of the 2016 revision of the WHO document in detecting cases of masked PV.

Distinguishing essential thrombocythemia JAK2V617F from polycythemia vera: limitations of erythrocyte values

Distinguishing essential thrombocythemia JAK2V617F from polycythemia vera is difficult because of shared mutation and phenotypic characteristics. The World Health Organization suggested hemoglobin and hematocrit values to diagnose polycythemia vera (PV), but their sensitivity and specificity were not tested. Moreover, red cell values do not accurately predict red cell mass, which we use to discriminate essential thrombocythemia JAK2V617F from PV. Eighty-three PV and 39 essential thrombocythemia JAK2V617F patients were diagnosed based on JAK2V617F positivity, chromium-51 red cell mass, and marrow biopsy findings. Red cell values used to construct a receiver operating characteristic analysis determined optimal thresholds for distinguishing essential thrombocythemia JAK2V617F from PV. Red cell value frequencies were plotted determining if overlap existed. Chromium-51 red cell mass separated PV from essential thrombocythemia JAK2V617F, but red cell values overlapped in 25.0-54.7%. Our data indicate that a significant proportion of PV patients may be underdiagnosed by using only red cell values. A bone marrow biopsy was performed in 199 of 410 (48.5%) and a serum erythropoietin value was measured in 225 of 410 (54.9%) of potential PV patients at our institution. Without isotope studies, marrow biopsies and serum erythropoietin values should improve diagnostic accuracy and become mandatory, but clinical data suggest these tests have not been routinely performed. Therefore, the clinical hematologist must be aware of imperfect accuracy when using only red cell values for distinguishing essential thrombocythemia JAK2V617F from PV.

European LeukemiaNet study on the reproducibility of bone marrow features in masked polycythemia vera and differentiation from essential thrombocythemia

The purpose of the study was to assess consensus and interobserver agreement among an international panel of six hematopathologists regarding characterization and reproducibility of bone marrow (BM) histologic features used to diagnose early stage myeloproliferative neoplasms, in particular differentiation of so-called masked/prodromal polycythemia vera (mPV) from JAK2-mutated essential thrombocythemia (ET). The six members of the hematopathology panel evaluated 98 BM specimens independently and in a blinded fashion without knowledge of clinical data. The specimens included 48 cases of mPV according to the originally published hemoglobin threshold values for this entity (male: 16.0-18.4 g/dL, female: 15.0-16.4 g/dL), 31 cases with overt PV according to the updated 2016 WHO criteria, and 19 control cases. The latter group included cases of JAK2-mutated ET, primary myelofibrosis, myelodysplastic syndrome, and various reactive conditions. Inter-rater agreement between the panelists was very high (overall agreement 92.6%, kappa 0.812), particularly with respect to separating mPV from ET. Virtually all cases of mPV were correctly classified as PV according to their BM morphology. In conclusion, a central blinded review of histology slides by six hematopathologists demonstrated that highly reproducible specific histological pattern characterize PV and confirmed the notion that there are no significant differences between mPV and overt PV in relation to BM morphology.

Optimal therapy for polycythemia vera and essential thrombocythemia: Preferred use of interferon therapy based on phase 2 trials

OBJECTIVES

To determine the value of recombinant interferon-alfa (rIFNα) in the treatment of polycythemia vera (PV) and essential thrombocythemia (ET) based on its biological activities and phase 2 clinical studies, pending completion of phase 3 trials; to determine importance of the Internet in patient decision-making in treatment selection.

RESULTS

The value of rIFNα in PV and ET is based upon its biological effects on PV stem cells and megakaryocyte proliferation. Single-arm trials are useful for life-threatening diseases when there are relatively few patients to evaluate endpoints, such as rIFNα treatment of PV and ET. Proper diagnostic criteria are mandatory; for PV, the current World Health Organization criteria emphasizing increased hemoglobin values exclude approximately one-third of eligible patients. Importance of these data: Single-arm studies in diseases exemplified by rIFNα in PV require updated diagnostic criteria for research and for clinical practice. The influence of the Internet on patient decisions for treatment is noteworthy.

CONCLUSION

The biologic basis for selecting therapy is exemplified by rIFNα in treating PV and ET. Current single-arm studies of rIFNα in PV and ET are relevant and acceptable. The importance of the Internet in patient decision-making is important.

Historical views, conventional approaches, and evolving management strategies for myeloproliferative neoplasms

The classical Philadelphia chromosome-negative myeloproliferative neoplasms (MPN), which include essential thrombocythemia, polycythemia vera, and myelofibrosis (MF), are in a new era of molecular diagnosis, ushered in by the identification of the JAK2(V617F) and cMPL mutations in 2005 and 2006, respectively, and the CALR mutations in 2013. Coupled with increased knowledge of disease pathogenesis and refined diagnostic criteria and prognostic scoring systems, a more nuanced appreciation has emerged of the burden of MPN in the United States, including the prevalence, symptom burden, and impact on quality of life. Biological advances in MPN have translated into the rapid development of novel therapeutics, culminating in the approval of the first treatment for MF, the JAK1/JAK2 inhibitor ruxolitinib. However, certain practical aspects of care, such as those regarding diagnosis, prevention of vascular events, choice of cytoreductive agent, and planning for therapies, present challenges for hematologists/oncologists, and are discussed in this article.

Polycythemia Vera: An Appraisal of the Biology and Management 10 Years After the Discovery of JAK2 V617F

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm that is associated with a substantial symptom burden, thrombohemorrhagic complications, and impaired survival. A decade after the seminal discovery of an activating mutation in the tyrosine kinase JAK2 in nearly all patients with PV, new treatment options are finally beginning to emerge, necessitating a critical reappraisal of the underlying pathogenesis and therapeutic modalities available for PV. Herein, we comprehensively review clinical aspects of PV including diagnostic considerations, natural history, and risk factors for thrombosis. We summarize recent studies delineating the genetic basis of PV, including their implications for evolution to myelofibrosis and secondary acute myeloid leukemia. We assess the quality of evidence to support the use of currently available therapies, including aspirin, phlebotomy, hydroxyurea, and interferon. We analyze recent studies evaluating the safety and efficacy of JAK inhibitors, such as ruxolitinib, and evaluate their role in the context of other available therapies for PV. This review provides a framework for practicing hematologists and oncologists to make rational treatment decisions for patients with PV.

Rationale for revision and proposed changes of the WHO diagnostic criteria for polycythemia vera, essential thrombocythemia and primary myelofibrosis

The 2001/2008 World Health Organization (WHO)-based diagnostic criteria for polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) were recently revised to accomodate new information on disease-specific mutations and underscore distinguishing morphologic features. In this context, it seems to be reasonable to compare first major diagnostic criteria of the former WHO classifications for myeloproliferative neoplasm (MPN) and then to focus on details that have been discussed and will be proposed for the upcoming revision of diagnostic guidelines. In PV, a characteristic bone marrow (BM) morphology was added as one of three major diagnostic criteria, which allowed lowering of the hemoglobin/hematocrit threshold for diagnosis, which is another major criterion, to 16.5 g/dl/49% in men and 16 g/dl/48% in women. The presence of a JAK2 mutation remains the third major diagnostic criterion in PV. Subnormal serum erythropoietin level is now the only minor criterion in PV and is used to capture JAK2-unmutated cases. In ET and PMF, mutations that are considered to confirm clonality and specific diagnosis now include CALR, in addition to JAK2 and MPL. Also in the 2015 discussed revision, overtly fibrotic PMF is clearly distinguished from early/prefibrotic PMF and each PMF variant now includes a separate list of diagnostic criteria. The main rationale for these changes was to enhance the distinction between so-called masked PV and JAK2-mutated ET and between ET and prefibrotic early PMF. The proposed changes also underscore the complementary role, as well as limitations of mutation analysis in morphologic diagnosis. On the other hand, discovery of new biological markers may probably be expected in the future to enhance discrimination of the different MPN subtypes in accordance with the histological BM patterns and corresponding clinical features.

Masked polycythaemia vera: presenting features, response to treatment and clinical outcomes

Masked polycythaemia vera (PV) has been proposed as a new entity with poorer outcome than overt PV. In this study, the initial clinical and laboratory characteristics, response to treatment and outcome of masked and overt PV were compared using red cell mass and haemoglobin or haematocrit levels for the distinction between both entities. Sixty-eight of 151 PV patients (45%) were classified as masked PV according to World Health Organisation diagnostic criteria, whereas 16 (11%) were classified as masked PV using the British Committee for Standards in Haematology (BCSH). In comparison with overt PV, a higher platelet count and a lower JAK2V617F allele burden at diagnosis were observed in masked PV. Patients with masked PV needed lower phlebotomies and responded faster to hydroxcarbamide than those with overt PV. Complete haematological response was more frequently achieved in masked than in overt PV (79% vs. 58%, P = 0.001). There were no significant differences in the duration of haematological response, the rate of resistance or intolerance to hydroxycarbamide and the probability of molecular response according to type of PV (masked vs. overt). Overall survival, rate of thrombosis and major bleeding, and probability of transformation was superimposable among patients with masked and overt PV.

Novel and emerging therapies for the treatment of polycythemia vera

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm defined by erythrocytosis and often accompanied by leukocytosis and thrombocytosis. Current treatment options, including IFN-α and hydroxyurea, effectively manage PV in many patients. However, some high-risk patients, particularly those who become hydroxyurea-intolerant/resistant, may benefit from IFN-α or new treatment options. A better understanding of PV pathophysiology, including the role of the JAK/STAT pathway, has inspired the development of new therapies. Several JAK inhibitors directly target JAK/STAT pathway activation and have been evaluated in Phase II/III trials with promising results. Pegylated variants of IFN-α, which reduce dosing frequency and toxicity associated with recombinant IFN-α, have yielded favorable efficacy results in Phase II trials. Finally, histone deacetylase inhibitors have been developed to manage PV at the level of chromatin-regulated gene expression. The earliest Phase III results from these next-generation therapies are expected in 2014.

Presence of calreticulin mutations in JAK2-negative polycythemia vera

Major CALR-mutated clones may be observed in polycythemia vera negative for JAK2 mutations.

Elevated serum erythropoietin in a patient with polycythaemia vera presenting with Budd-Chiari syndrome

Polycythaemia vera (PV) is a clonal disorder of bone marrow stem cells characterised by erythrocytosis. Diagnosis of PV requires exclusion of secondary causes of polycythaemia. It has been held that an elevated erythropoietin (Epo) level strongly indicates secondary erythrocytosis and excludes PV diagnosis, to the extent that the reduced serum Epo level is currently listed as a minor criterion in the WHO classification scheme for PV. However, patients with PV who co-present with Budd-Chiari syndrome have been documented with elevated serum Epo levels. For these patients, identification of the Janus kinase 2 (JAK2) V617F point mutation along with the transient nature of the Epo elevation provides certainty of PV diagnosis, as illustrated by the proband. In this case report, the patient's positive response to cytoreductive therapy (hydroxyurea 500 mg daily) and phlebotomy (750 mL over three phlebotomies) further supports validity of PV diagnosis with elevated Epo. The patient remains on rivaroxaban (Xarelto) for treatment of her portal vein thrombosis.

WHO classification of myeloproliferative neoplasms (MPN): A critical update

Although the revised World Health Organization (WHO) criteria for the diagnosis and classification of myeloproliferative neoplasms (MPN) were defined by a panel of expert hematopathologists and clinicians, controversy has been repeatedly expressed questioning the clinical usefulness and reproducibility of these diagnostic guidelines. In particular, the distinction between essential thrombocythemia (ET), early/prefibrotic primary myelofibrosis (PMF) and initial stages of polycythemia vera (PV) is still a matter of debate. In this context, it has been argued that clinical correlations with histological features were not firmly substantiated. On the other hand, recently published data from independently performed studies have repeatedly validated the reproducibility of the WHO criteria and provided persuasive evidence that discrimination of early/prefibrotic PMF has a significant impact on the risk of myelofibrotic and leukemic transformation. However, as has been explicitly required, the WHO concept is based on the recognition of characteristic bone marrow patterns and a consensus of clinical and molecular data.

Application of the optimized CO-rebreathing method for determination of hemoglobin mass in patients with polycythemia vera

Determination of red cell volume (RCV) might contribute to establishing the diagnosis of polycythemia vera (PV). A novel simplified method to detect RCV through CO rebreathing is nowadays applied in healthy young individuals but was not tested in a clinical or PV setting. The aim of the present study is to evaluate whether this spirometric approach is applicable in older subjects and contributes to PV diagnosis in a proof-of-concept approach. At first, RCV was determined by the optimized CO-rebreathing method in healthy subjects >50 years of age (n = 81, age 66 ± 9 years). Failure rate and age distribution of subjects who failed with CO rebreathing were analyzed. Then, RCV was measured in male PV patients (n = 7) and compared to healthy male controls (n = 35). RCV values in relation to several anthropometric references (body weight, body surface area (BSA), lean body mass (LBM)) were calculated to determine the sensitivity and specificity of established RCV thresholds when using optimized CO rebreathing. In healthy subjects, test failure rate was 9.9 %, but failure was not associated with age. Sensitivity and specificity (sens/spec) to detect PV was 100 %/83 % using the criteria of the PV study group. Using criteria based on BSA, sens/spec was 14 %/100 %. An arbitrary threshold of 50 ml/kg LBM yielded sens/spec of 100 %/97 %. In conclusion, this proof-of-concept indicates that optimized CO rebreathing is applicable in older subjects and allows determining RCV for the diagnosis of PV. Normalized values for RCV measures obtained from CO rebreathing are needed to grant sufficient sensitivity and/or specificity.

Masked polycythemia vera diagnosed according to WHO and BCSH classification

Polycythemia vera (PV) is currently diagnosed by the World Health Organization (WHO) criteria regarding hemoglobin (HB) levels and JAK2V617F and related mutations or by the British Committee for Standards in Haematology (BCSH) guidelines predominantly based on hematocrit (HCT) values (>52% in men and >48% in women) in JAK2 mutated patients. We examined clinical features at diagnosis and outcome in 397 mutated PV patients showing a bone marrow (BM) morphology conforming with the WHO descriptions but including also cases with a HB level <18.5 g/dL in males (range 16.0-18.4) and <16.5 g/dL in females (range 15.0-16.4). These patients were regarded as masked PV (mPV) comprising 140 (35%) cases of our cohort. A comparison with the BCSH criteria based on HCT levels revealed a decrease of mPV patients to 59 (15%). In both classification systems, mPV patients were more males, presented more frequently with higher platelet counts, and increased BM reticulin fibrosis. A worsening of overall survival was documented in mPV patients in comparison with overt PV following the WHO (P = 0.011) as well as the BCSH (P = 0.0019) criteria. Risk factors for inferior survival in mPV were age >65 years and white blood cell count >15 × 10(9) /L. Without these risk factors mPV patients had the same survival as overt PV suggesting that a fraction of patients with HB lower than that required for WHO diagnosis should still be considered as overt PV. This study has established the existence of mPV by two different classification systems based on either HB or HCT threshold values.

Masked polycythemia vera (mPV): results of an international study

We examined the baseline features and clinical outcomes of 140 patients presenting with JAK2V617F positivity and a bone marrow morphology conforming with WHO criteria of polycythemia vera (PV), but a hemoglobin level of <18.5 g/dL in males (range 16.0-18.4) and <16.5 g/dL in females (range 15.0-16.4). This cohort operationally referred to as masked PV (mPV) was compared with 257 patients with overt PV and displayed male predominance, a more frequent history of arterial thrombosis and thrombocytosis. Incidence of thrombosis was similar between the two groups but mPV displayed significantly higher rates of progression to myelofibrosis and acute leukemia and inferior survival. In multivariable analysis mPV diagnosis was an independent predictor of poor survival along with age >65 years and leukocyte count >10 × 10(9) /L. Our data suggest that mPV is a heterogeneous myeloproliferative neoplasia and not necessarily an early/ pre-polycythemic form of classical PV that at onset in a small fraction of patients clinically may mimic essential thrombocythemia. On the other hand, the majority mPV may have a longer prodrome of undiagnosed PV or a disease biology akin to primary myelofibrosis-post PV myelofibrosis that could explain the worsening of outcome in comparison to overt/classical manifestations.

Evaluation of WHO criteria for diagnosis of polycythemia vera: a prospective analysis

We prospectively evaluated the accuracy of the 2007 World Health Organization (WHO) criteria for diagnosing polycythemia vera (PV), especially in "early-stage" patients. A total of 28 of 30 patients were diagnosed as PV owing to an elevated Cr-51 red cell mass (RCM), JAK2 positivity, and at least 1 minor criterion. A total of 18 PV patients did not meet the WHO criterion for an increased hemoglobin value and 8 did not meet the WHO criterion for an increased hematocrit value. Bone marrow morphology was very valuable for diagnosis. Low serum erythropoietin (EPO) values were specific for PV, but normal EPO values were found at presentation (20%). We recommend revision of the WHO criteria, especially to distinguish early-stage PV from essential thrombocythemia. Major criteria remain JAK2 positivity and increased red cell volume, but Cr-51 RCM is mandatory for patients who do not meet the defined elevated hemoglobin or hematocrit value (>18.5 g/dL and 60% in men and >16.5 g/dL and 56% in women, respectively). Minor criteria remain bone marrow histology or a low serum EPO value. For patients with a normal EPO value, marrow examination is mandatory for diagnostic confirmation. Because the therapies for myeloproliferative disorders differ, our data have major clinical implications.

Interferon and the treatment of polycythemia vera, essential thrombocythemia and myelofibrosis

Recombinant IFN-α (rIFN-α) induces complete hematologic remissions in patients with myeloproliferative neoplasms (MPNs), but its use has been limited by side effects owing to the relatively high doses used. Now, low-dose rIFN-α is stressed, starting relatively early in the course of the MPNs. In polycythemia vera, this has resulted in a significant clinical, hematologic, morphologic and molecular response manifested by reduction in the JAK2(V617F) allele burden, sustained even after discontinuation of recombinant IFN. In essential thrombocythemia, platelet count reduction is prompt and durable without treatment for varying periods. In hypercellular primary myelofibrosis, rIFN-α has restored normal blood counts, reduced splenomegaly and induced morphologic marrow remissions. This article highlights our current use of rIFN-α in MPNs.