Refractory anaemia with excess of blasts (RAEB): analysis of reclassification according to the WHO proposals.

The French-American-British (FAB) classification assigns patients with myelodysplastic syndromes to the category of refractory anaemia with excess blasts (RAEB) if they have a medullary blast count of 5-20%, and/or a peripheral blast count of 2-5%. The new World Health Organization (WHO) classification subdivides RAEB into RAEB I with a medullary blast count < or =10% and a peripheral blast count < or =5% and RAEB II with >10% medullary and/or >5% peripheral blasts. RAEB II is also diagnosed if Auer rods are present. In 558 patients, we analysed these subtypes of RAEB in terms of haematological characteristics, karyotype anomalies and prognosis. RAEB I was diagnosed in 256 and RAEB II in 302 patients. In the RAEB II group, 22% of patients had >5% peripheral blasts or the presence of Auer rods. The median survival was 16 months for RAEB I as compared with 9 months for RAEB II. Patients with Auer rods, regardless of their medullary and peripheral blast count, had no worse prognosis. No significant differences were identified between the RAEB subtypes with respect to clinical, morphological, haematological and cytogenetic parameters. The survival data support the WHO reclassification of RAEB based on peripheral and medullary blast counts and Auer rods. The WHO classification is useful for diagnosis and provides risk stratification, supported by cytogenetic data for clinical decision making, identifying those RAEB patients with an unfavourable prognosis who should be offered chemotherapy or stem cell transplantation.