Myelodysplastic syndromes (MDS) are clonal bone marrow neoplasms characterized by dysplasia and ineffective hematopoiesis leading to peripheral blood cytopenias, with an increased risk of progression to acute myeloid leukemia. The conventional diagnostic work-up of MDS relies on cytomorphological evaluation of bone marrow, which may be complemented by conventional cytogenetic, flow cytometry, and molecular analysis by next generation sequencing techniques. Suspicion of MDS is the commonest reason for bone marrow aspirate in older patients with unexplained peripheral blood cytopenias. Yet many patients are exposed to unnecessary bone marrow aspiration-related discomfort and harms, because of the limited prevalence of disease among subjects referred for suspected MDS. In this context, a valid and reliable assay based on peripheral blood sample that accurately discriminates MDS from other cytopenia etiologies without requiring invasive bone marrow aspiration is warranted. The accuracy of peripheral blood neutrophil myeloperoxidase expression quantified by flow cytometric analysis for the diagnosis of MDS is supported by three primary studies totaling 211 individuals. An intra-individual robust coefficient of variation (RCV) value for neutrophil myeloperoxidase expression lower than 30.0% accurately ruled out MDS, with both sensitivity and negative predictive value point estimates of 100%, in consecutive patients with suspected disease. This biomarker might obviate the need for cytomorphological evaluation of bone marrow aspirate for up to 35% of patients referred for suspected MDS. Although promising, these preliminary results require replication in an independent external validation sample. The broad aim of the multicenter MPO-MDS-Valid study project is to prospectively validate the diagnostic accuracy of intra-individual RCV for peripheral blood neutrophil myeloperoxidase expression quantified by flow cytometric analysis among consecutive patients referred for suspected MDS.