Flow Cytometric Analysis of Peripheral Blood Neutrophil Myeloperoxidase Expression and Myelodysplastic Syndromes

The primary objective of MPO-MDS-pilot study is to estimate the accuracy of flow cytometric analysis of neutrophil myeloperoxidase expression in peripheral blood for the diagnosis of myelodysplastic syndromes (MDS) and/or chronic myelomonocytic leukemia (CMML).

The secondary objectives are:

• to provide accuracy estimates for prespecified thresholds of neutrophil myeloperoxidase expression in peripheral blood in ruling out MDS and/or CMML.
• to estimate the prevalence of alternate diagnosis established by bone marrow cytomorphology.

The MPO-MDS-pilot project is a multicenter, phase II, cross-sectional, diagnostic accuracy study of consecutive unselected patients referred for suspected MDS or CMML.

Screening: All consecutive patients referred to the immuno-hematology lab at the study sites for suspicion of MDS will be screened for eligibility. A lab physician will review inclusion and exclusion criteria, using computerized medical and laboratory records.

Recruitment: Participants will be included in the study once all the screening activities have been conducted and only if the patient meets all inclusion and none exclusion criteria. The consent for flow cytometry analysis of peripheral blood sample and data collection through chart review will be sought under a regime of "non-opposition" (opt-out): after appropriate written information is delivered, cross-sectional data will be collected except in case of opposition from the patient. All patients included in the study will be assigned a unique patient identification number. This number will be used to identify the patient throughout the study.

Index test: Flow cytometry analysis of neutrophil myeloperoxidase expression in peripheral blood will be performed within 24 h of MDS diagnostic evaluation and blinded to the reference standard.

Reference standard: The diagnosis of MDS will be established according to the World Health Organization (WHO) classification, based on clinical data, peripheral blood cytopenia, cytomorphology of peripheral blood and bone marrow aspirate, and cytogenetic analysis. The criteria for MDS diagnosis are 1) the presence of ≥10% dysplastic cells in any hematopoietic lineage, 2) the exclusion of acute myeloid leukemia (defined by the presence of ≥20% peripheral blood or bone marrow blasts), and 3) the exclusion of reactive etiologies of dysplasia. Cytopenia is defined by hemoglobin concentration <10 g/dL, platelet count <100x109/L, and/or absolute neutrophil count <1.8 x109/L. Yet a diagnosis of MDS could be made with milder levels of cytopenia. Idiopathic cytopenia of uncertain significance (ICUS) is defined by unexplained mild persistent cytopenia for at least 6 months and the failure to establish the diagnosis to MDS according to published guidelines. Consistent with WHO classification, MDS subcategorization will rely on the degree of dysplasia (unilineage versus multilineage), blast percentages, presence of ring sideroblasts, and cytogenetic analysis (del(5q)). The criteria for CMML diagnosis are 1) the presence of persistent peripheral blood monocytosis ≥1 x109/L, and 2) monocyte accounting for more than 10% of the white blood cell differential count. Evaluation of bone marrow cytomorphology will be performed prospectively by experienced hematopathologists who are blinded to the index test results.

Patients with confirmed suspicion of MDS: Participants for whom the diagnosis of MDS (or CMML) is confirmed by the reference standard will be categorized as patients with confirmed suspicion of MDS.

Patients with unconfirmed suspicion of MDS: Participants for whom the diagnosis of MDS (or CMML) is ruled out by the reference standard will be categorized as patients with unconfirmed suspicion of MDS. This latter subgroup will include patients with ICUS, as defined in accordance with published guidelines

Follow-up: No follow-up visit is planned in this cross-sectional diagnostic accuracy study.

Inclusion criteria

• Age ≥50 years;
• Clinical suspicion of myelodysplastic syndromes (MDS) and / or chronic myelomonocytic leukemia (CMML);
• Peripheral blood cytopenia defined by hemoglobin concentration <10 g/dL, platelet count <100 x109/L, and/or absolute neutrophil count <1.8 x109/L.

Exclusion criteria

• History of or active documented MDS or CMML;
• Admission to the intensive care unit;
• Suspicion of hematological disease other than MDS requiring bone marrow aspirate and/or biopsy (i.e., acute leukemia,…);
• Absolute neutrophil count <0.5 x109/L;
• Not affiliated with a social security system;
• Homelessness;
• Incarcerated;
• Inability to understand research information and/or to provide non-opposition, because of language restriction, dementia, or altered mental status;
• Refusal to participate;
• Previous enrollment in the study.