Flow Cytometry Applications in the Diagnosis of Myelodysplastic Syndrome (MDS): Analysis of 45 Cases.

Flow cytometry is a widely used method to study most of the hematologic malignancies. The utility of bone marrow immunophenotyping for the evaluation of patients with myelodisplastic syndrome (MDS) is currently being evaluated but most of these studies are based on the analysis of a large number of monoclonal antibodies.

OBJECTIVE: To explore the potential contribution of flow cytometry to the diagnosis of MDS using a reduced panel of conjugated monoclonal antibodies (MoAb).

PATIENTS AND METHODS: 45 bone marrow specimens from patients with a diagnosis of MDS based on morphologic and cytogenetic parameters (17 RA, 12 RARS, 5 MMCL, 9 RAEB, 2 RAEB-t), were analyzed by flow cytometry. In addition, 25 samples of bone marrow obtained from patients with cytopenias, but no diagnosis of MDS, were also studied. The panel of MoAb used was designed to identify abnormalities in the differentiation pathways of erithroid (CD71 FITC/Gly A PE/CD45 PC5) and myeloid lineage (CD 16 FITC/CD11b PE/CD13 PC5) as well as the presence of specific aberrant features in the CD34+ myeloid cell population (TdT FITC/CD7 PE/CD34 PC5). All samples were analized by two independet observers. To establish the diagnosis of MDS by flow cytometry, it was necessary to describe either immunophenotypic abnormalities in both myeloid and erithroid lineages or abnormalities in only one lineage plus description of more than 5% of CD34+ cells or abnormalities in one lineage plus description of aberrant features in the CD34+ population, regardless of its percentage.

RESULTS: In 43 of the 45 samples analyzed, flow cytometric criteria of MDS were described. Only two cases (1 RARS with normal karyotype and 1 RA with complex cytogenetics) were considered normal according to the immunophenotypic criteria (95% sensivity). Regarding the cohort control, 4 samples had flow cytometric criteria of MDS; 11 samples showed isolated antigenic aberrancies in the erithroid differentiation and the 11 samples left were considered as normal.

CONCLUSIONS: Flow cytometry may be a useful tool in the diagnosis of MDS, even analysing only two hemopoietic cell lineages. The reduced panel of MoAb described here can be widely used, is easy to be applied and shows a high sensitivity and a low cost. However, the finding of isolated immunophenotypic abnormalities in some patients without cytologic data of MDS seems to negatively influence the specificity of the technique. Nevertheless, those cases presenting an abnormal immunophenotype and normal morphology should be carefully monitored during their ulterior follow-up.