title: European Bone Marrow Working Group trial on reproducibility of World Health Organization criteria to discriminate essential thrombocythemia from prefibrotic primary myelofibrosis.
abstract: BACKGROUND
  The World Health Organization classification of myeloproliferative neoplasms discriminates between essential thrombocythemia and the prefibrotic phase of primary myelofibrosis. This discrimination is clinically relevant because essential thrombocythemia is associated with a favorable prognosis whereas patients with primary myelofibrosis have a higher risk of progression to myelofibrosis or blast crisis.
  
  
  METHODS
  To assess the reproducibility of the classification, six hematopathologists from five European countries re-classified 102 non-fibrotic bone marrow trephines, obtained because of sustained thrombocytosis.
  
  
  RESULTS
  Consensus on histological classification defined as at least four identical diagnoses occurred for 63% of the samples. Inter-observer agreement showed low to moderate kappa values (0.28 to 0.57, average 0.41). The percentage of unclassifiable myeloproliferative neoplasms rose from 2% to 23% when minor criteria for primary myelofibrosis were taken into account. In contrast, the frequency of primary myelofibrosis dropped from 23% to 7%, indicating that the majority of patients with a histological diagnosis of primary myelofibrosis did not fulfill the complete criteria for this disease. Thus, over 50% of cases in this series either could not be reproducibly classified or fell into the category of unclassifiable myeloproliferative neoplasms.
  
  
  CONCLUSIONS
  World Health Organization criteria for discrimination of essential thrombocythemia from prefibrotic primary myelofibrosis are poorly to only moderately reproducible and lead to a higher proportion of non-classifiable myeloproliferative neoplasms than histology alone.
authors: Institute of Pathology, Medizinische Hochschule, Carl Neuberg Str. 1 30625 Hannover, Germany.
authors: Thomas
authors: T
authors: Buhr
authors: Konnie
authors: K
authors: Hebeda
authors: Vassiliki
authors: V
authors: Kaloutsi
authors: Anna
authors: A
authors: Porwit
authors: Jon
authors: J
authors: Van der Walt
authors: Hans
authors: H
authors: Kreipe
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005060:Europe; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009196:Myeloproliferative Disorders / Q000145:classification / Q000175:diagnosis; D055728:Primary Myelofibrosis / Q000175:diagnosis*; D011379:Prognosis; D015203:Reproducibility of Results; D013920:Thrombocythemia, Essential / Q000175:diagnosis*; D014944:World Health Organization; D055815:Young Adult