V. Diagnosis (a) Diagnosis He Guangsheng, Department of Hematology, The First Affiliated Hospital of Nanjing Medical University There is no gold standard for the diagnosis of MDS, which requires a comprehensive and dynamic clinical judgment of the presence of abnormal clonal and refractory hematocrit. The first requirement is: ① persistent hematocrit reduction for more than 6 months (hemoglobin <110g/L, absolute neutrophil value <1.5×10<9/L, platelets <100×10<9/L), and ② exclusion of other disorders. If the patient does not meet one more definite condition, MDS can be diagnosed. if the patient does not meet the definite condition, MDS auxiliary diagnostic criteria test will be performed, and the diagnosis of highly suspected MDS will be made and follow-up will be continued. after the diagnosis of MDS is clear, further typing diagnosis will be performed. Differential diagnosis At present, there is no "gold standard" for the diagnosis of MDS, and it is often necessary to differentiate it from the following diseases: (a) chronic aplastic anemia (CAA). The difference between CAA and MDS is that the reticulocytes in MDS are generally not low, and nucleated erythrocytes or naive granulocytes can be seen in peripheral blood; the percentage of early bone marrow cells is not low or increased, and pathological hematopoiesis is obvious, and chromosomal karyotype abnormalities can be found. In contrast, CAA bone marrow granules contain mainly non-hematopoietic cells, and the karyotype is basically normal. (ii) Immune-related hematocritopenia (IRP). Autoantibodies on bone marrow hematopoietic cells can be detected, and the response to treatment with glucocorticoids and immunosuppressants is rapid and effective. (iii) Paroxysmal sleep hemoglobinuria (PNH). Hematocrit and pathological hematopoiesis may also be present, but PNH clonal cells are detected by flow cytometry and most have a positive Ham test as well as intravascular hemolytic changes. (iv) Megaloblastic anemia. The cell morphology is megaloblastic and can be easily confused with MDS. MDS supplementation of folic acid and vitamin B12 levels does not improve hematopoiesis and morbid hematopoiesis. (v) Hypoproliferative AML. the percentage of RAEB subtype primitive cells is increased in MDS, but is less than 20%. Conditions I. Necessary conditions (both conditions must be present at the same time, one cannot be absent) 1. Persistent (≥6 months) hematocrit of one or more lineages: erythroid lineage (Hb<110g/L); neutrophil lineage (ANC<1.5×10<9/L); megakaryocytic lineage (PLT<100×10<9/L) 2. Exclusion of other hematopoietic and non-hematopoietic that can lead to hematocrit or pathological hematopoiesis The diagnosis of MDS can be confirmed when the two "required conditions" and at least one "definite condition" are met. 2. Primitive cells: 5-19% in the bone marrow smear 3. Typical chromosomal abnormalities (conventional karyotype analysis or FISH) 3. Ancillary conditions Those who meet the necessary conditions but do not meet the definitive conditions but have typical clinical manifestations of MDS are highly suspected of having MDS (HS-MDS) 1. The presence of monoclonal cell populations in the erythroid or/and myeloid lineages 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