OBJECTIVETo apply the WHO criteria and the minimal diagnostic criteria to the classification of myelodysplastic syndromes (MDS) with low percentage (< 0.050) bone marrow (BM) blasts.

METHODSTwo hundred and ten MDS patients with less than 0.050 BM blasts diagnosed between 1988 and 2005 according to FAB criteria were retrospectively reclassified with WHO criteria (2001) and minimal diagnostic criteria.

RESULTSAccording to the WHO criteria, 5 patients were diagnosed as refractory anemia (RA), 7 as refractory anemia with ringed sideroblasts (RARS), 76 as refractory cytopenia with multilineage dysplasia (RCMD), 9 as RCMD-RS, 35 as MDS-unclassified (MDS-U), 3 as 5q - syndromes, and the rest 75 patients could not be classified suitably. Among the latter 75 patients 16 BM smears showed dysplasia in more than 2 cell lineage but only unilineage cytopenia in peripheral blood (PB). Nine of them were reclassified as RCMD after followed up for more than half a year. Forty-four BM smears showed erythroid dysplasia only, but bicytopenia or pancytopenia in PB. Twenty-seven of them were classified as RCMD after follow-up. Fifteen BM smears not showed dysplasia in any myeloid lineage were reclassified as MDS (5 patients), HS-MDS (5 patients) and idiopathic cytopenia of uncertain significance (ICUS) (5 patients) according to the MDS minimal diagnostic criteria.

CONCLUSIONAccording to WHO criteria (2001), RA is the least diagnosis in MDS. The minimal diagnostic criteria for MDS classification of patients not fulfilled the standard criteria of MDS.