Experts representing the NCCN, the International Working Group (IWG) on MDS, and the European Leukemia Network (ELN) presented new recommendations for diagnostic criteria for MDS in Vienna. Two necessary conditions are first met for the diagnosis of MDS: persistent hematocrit and exclusion of other disorders. Developmental abnormalities (morphologically diseased hematopoiesis) are excluded from the necessary criteria and are only one of three definitive criteria: 1. Developmental abnormalities: at least 10% of any of the erythroid lineage, neutrophil lineage, and megakaryocyte lineage in the bone marrow smear; >15% of ringed iron granulocytes; 2. Primitive cells: consistently between 5 and 19% in the bone marrow smear; 3. Typical chromosomal abnormalities (conventional karyotyping or FISH). In contrast, according to the recommendations, the diagnosis of MDS requires that two necessary conditions and one definitive criterion be met. When the patient does not meet the definitive criteria, such as: atypical karyotype abnormalities, developmental abnormalities (morphologically sick hematopoiesis) <10%, primitive cell percentage 4%, etc., and the clinical presentation is highly suspicious of MDS, such as transfusion-dependent macrocytic anemia, the test of MDS auxiliary diagnostic criteria should be performed, and those who meet them are basically clonal myeloid neoplasms with bone marrow failure, and such patients are diagnosed as highly suspicious of MDS is a clonal myeloid neoplasm with bone marrow failure, which is basically defined as MDS in China, but the Vienna criteria classify it as highly suspected MDS because the patient does not meet the definitive criteria, and recommend follow-up until the definitive criteria are met, showing a rare rigor. Therefore, although the adoption of the Vienna criteria for adjunctive criteria will increase the number of suspected MDS cases, the threshold for definitive MDS diagnosis is still strictly grasped. If the ancillary tests are not performed, or if the results are negative, the patient is followed up with periodic examinations to clarify the diagnosis. Minimum diagnostic criteria conditions for MDS: I. Essential criteria: 1. Persistent (≥ 6 months) mono- or multilineage hematocrit: erythrocytes (Hb < 110 g/L); neutrophils (ANC < 1.5 × 109/L); megakaryocytes (BPC < 100 × 109/L). 2. Exclude other hematopoietic and non-hematopoietic system disorders that can lead to hematocrit reduction or abnormal development . 1. Developmental abnormalities: bone marrow smear with at least 10% of erythroid, neutrophil, and megakaryocyte lineages; >15% of ringed iron granulocytes. 2. Primitive cells: 5 to 19% in bone marrow smear. 3. Typical chromosomal abnormalities (conventional karyotype analysis or FISH). Ancillary criteria (for those who meet the necessary criteria but do not meet the definitive criteria but have typical clinical manifestations of MDS, such as transfusion-dependent macrocytic anemia): 1. Abnormal bone marrow cell phenotype on flow cytometry, suggesting the presence of a monoclonal cell population in the erythroid lineage or/and myeloid lineage. 2. The presence of clear molecular markers of monoclonal cell populations: HUMARA analysis, gene chip profiling or point mutations (e.g. RAS mutations). 3, Significant and persistent reduction in CFU colony (± cluster) formation in bone marrow or/and circulating progenitor cells.