Abstract: Objective To explore the significance of the number of circulating CD34+ cells in the peripheral blood from patients with myelodysplastic syndromes（MDS） on disease subtype and prognosis. Methods The percentage and absolute count of circulating CD34+ cells of the 16 healthy individuals and 40 patients with MDS were measured by flow cytometry. Forty patients with MDS were divided into RA／RARS／RCMD subgroup or RAEB Ⅰ／RAEB Ⅱ subgroup； favorable chromosomal subgroup， intermediate chromosomal subgroup and poor chromosomal subgroup；intermediate-risk Ⅰ subgroup， intermediaterisk Ⅱ subgroup and highrisk subgroup according to WHO classification， chromosomal abnormalities and international prognostic scoring system（IPSS）. Results The percentage and the absolute count of circulating CD34+ cells in peripheral blood from patients with MDS were 0.67％ and 17.24 cells／μl， while they were 0.03％ and 1.63cells／μl in normal control（both P＜0.01）. In MDS group： the percentage and the absolute count of CD34+ cells in RA／RARS／RCMD subgroup were 0.05％ and 3.50 cells／μl，which were lower than 3.09％ and 81.95 cells／μl in RAEB Ⅰ／RAEB Ⅱ subgroup（both P＜0.01）. The percentage and the absolute count of CD34+ cells in favorable chromosomal subgroup were 0.05％ and 3.50 cells／μl， while they were 1.29％ and 18.23 cells／μl in intermediate subgroup and 3.09％ and 133.10 cells／μl in poor chromosomal subgroup, respectively. With the emergence of chromosomal abnormalities, the percentage and absolute count were gradually increased（P＜0.05）. The percentage and the absolute count of CD34+ cells in intermediaterisk Ⅰ（0.05％ and 3.50 cells／μl），intermediaterisk Ⅱ（1.57％ and 35.55 cells／μl） and highrisk subgroup（8.15％ and 192.05 cells／μl） were gradually increased with the progressive increase of IPSS score（all P＜0.01）.
Conclusion Detection of the number of circulating CD34+ cells in peripheral blood cells may be a useful tool for subtyping and predicting the prognosis of MDS.