Utility of a Single-Tube, Six-Color Flow Cytometry Panel for the Diagnosis of Myelodysplastic Syndrome: Experience of a Tertiary Care Centre in India

Background: Diagnosis of myelodysplastic syndromes (MDS) is challenging in the presence of morphological mimickers. Flow cytometric immunophenotyping (FCI) has been added to the diagnostic armamentarium, but its use in clinical practice is variable. Materials and Methods: Bone marrow aspirate samples from 54 patients with a clinical and/or morphological suspicion of MDS were subjected to FCI using a single-tube, 6-colour panel comprising of monoclonal antibodies against CD13, CD11b, CD16, CD34, CD45 and CD56. Analysis was centered on the abnormal maturation pattern of granulocytes, blast percentage (≥3%) and ratio of side scatter peak channel value (SSC-PCV) of granulocytes and lymphocytes. Each of these parameters was assigned a score of 1. Overall sensitivity and specificity of this panel was ascertained to differentiate cytopenia/s of MDS from non-MDS cases. Results: Forty MDS and 14 non-MDS cases were diagnosed based on morphology and cytogenetic results. Twenty control samples were also processed simultaneously for FCI to assign the cutoff for various flow cytometric parameters. A score ≥2 was defined as positive for MDS. Hypogranularity was present in 62.5% cases of MDS. The median SSC-PCV of granulocytes and lymphocytes was 6.16 in the MDS group, 7.9 in the non-MDS group and 8.90 in the control group (p <0.05). This cut-off value of 6.16 had a specificity of 92.5% based on the ROC curve analysis. Abnormal granulocyte maturation patterns for CD13/16, CD13/11b and CD11b/16 dot plots were observed in 95.3, 69.8 and 74.4% cases, respectively. The overall sensitivity and specificity of the panel was found to be 87.5% and 64.2%, respectively. Conclusion: FCI is now an important tool for diagnostic workup in patients presenting with persistent cytopenia with or without morphological evidence of dyspoiesis. Inclusion of objective parameters like SSC-PCV would also reduce inter-lab variability in MDS diagnosis.