1. Background The myeloproliferative neoplasms (MPNs) are a heterogeneous group of diseases characterised by overproduction of one or more myeloid cell types via bone marrow stimulation. Entities include; Polycythaemia vera, (PV) Essential thrombocythaemia (ET) Primary (idiopathic) myelofibrosis (PMF) The JAK2V617F mutation is central to all three disease entities. These diseases possess specific genetic lesions and clinical characteristics. There are currently no definitive incidence rates available. Conclusion  The included studies showed high heterogeneity, demonstrating that the reported incidence rates are unlikely to be measuring a single, true underlying value of incidence rates.  The pooled incidence rates reflect the rarity of MPNs in the general population.  Improved, widespread registration of MPNs would provide better information for global comparison of the incidence of these diseases which will be relevant to clinician’s and guide further service development and scientific research. Methods Embase, Medline, PubMed and Web of Science databases were searched for articles reporting incidence rates for MPNs. No language or other restrictions were imposed. A random effects meta-analysis was undertaken to produce combined incidence rates for PV, ET and PMF. Heterogeneity was assessed using the I 2 statistic. Publication bias assessed using Begg-Mazumdar and Egger tests. Results How common are the Myeloproliferative Neoplasms: A Systematic review and Meta-Analysis. Glen J Titmarsh 1, Andrew Duncombe 2, Mary Frances McMullin 3, Michael O’Rorke 1, Ruben Mesa 4, Frank De Vocht 5, Sarah Horan 6, Lin Fritschi 7, Mike Clarke 1, Lesley A Anderson 1. 1 Centre for Public Health, Queen’s University Belfast, Northern Ireland. 2 Department of Haematology, University of Southampton, UK. 3 Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Northern Ireland. 4 Mayo Clinic Cancer Centre. Arizona. USA. 5 School of Social and Community Medicine. University of Bristol, UK 6 School of Health Sciences. City University London, UK. 7 School of Public Health, Epidemiology and Biostatistics. Curtin University. Australia Polycythaemia Vera (PV) Essential Thrombocythaemia (ET) Primary Myelofibrosis (PMF) Classic Myeloproliferative Neoplasms (MPNs) Combined Pooled Crude Rate Per 100,000 Per Year (95% CI) 0.84 (0.70 – 1.01) 1.03 (0.58 – 1.80) 0.47 (0.34 – 0.65) 2.58 (1.90 – 3.50) Incidence Range per 100,000 0.01 to 2.610.21 to 2.270.22 to 0.991.15 to 4.99 I2I2 99.1%99.6%97.1%99.6% Publication bias Begg’s Test p-value 0.6740.2101.000 Egger’s Test p-value 0.2370.007<0.0010.039 Gender Pooled Crude Male Rate Per 100,000 Per Year (95% CI) 0.87 (0.58 – 1.30) 1.44 (0.81 – 2.53) 0.59 (0.39 – 0.90) 2.56 (1.12 – 5.81) Pooled Crude Female Rate Per 100,000 Per Year (95% CI) 0.73 (0.46 – 1.15) 2.12 (1.27 – 3.54) 0.30 (0.22 – 0.42) 2.27 (0.95 – 5.42) Time Period Pooled Crude Rate Per 100,000 Per Year Pre 2005 (95% CI) 0.84 (0.70 – 1.01) 1.01 (0.58 – 1.75) 0.49 (0.34 – 0.70) 2.52 (1.91 – 3.33)