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.