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Chronic Myeloproliferative Disorder

A unified definition of clinical resistance/intolerance to hydroxyurea in essential thrombocythemia: results of a consensus process by an international working group

A Corrigendum to this article was published on 25 April 2007


A widely accepted definition of resistance or intolerance to hydroxyurea (HU) in patients with essential thrombocythemia (ET) is lacking. An international working group (WG) was convened to develop a consensus formulation of clinically significant criteria for defining resistance/intolerance to HU in ET. To this aim, an analytic hierarchy process (AHP), a multiple-attribute decision-making technique, was used. The steps consisted of selecting the candidate criteria for defining resistance/intolerance; identifying the motivations that could influence the preference of the WG for any individual criterion; comparing the candidate criteria in a pair-wise manner; and grading them according their ability to fulfill the motivations. Every step in the model was derived by questionnaires or group discussion. The WG proposed that the definition of resistance/intolerance should require the fulfillment of at least one of the following criteria: platelet count greater than 600 000/μl after 3 months of at least 2 g/day of HU (2.5 g/day in patients with a body weight over 80 kg); platelet count greater than 400 000/μl and WBC less than 2500/μl or Hb less than 10 g/dl at any dose of HU; presence of leg ulcers or other unacceptable muco-cutaneous manifestations at any dose of HU; HU-related fever.

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This work was based on an initiative of the European LeukemiaNet within the 6th European Community Framework Programme for Research and Technological Development. This work was supported by a grant from Shire.

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Correspondence to G Barosi.

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Barosi, G., Besses, C., Birgegard, G. et al. A unified definition of clinical resistance/intolerance to hydroxyurea in essential thrombocythemia: results of a consensus process by an international working group. Leukemia 21, 277–280 (2007).

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  • essential thrombocythemia
  • hydroxyurea
  • analytic hierarchy process
  • resistance
  • intolerance

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