Flow cytometric analysis of peripheral blood neutrophil myeloperoxidase expression for ruling out myelodysplastic syndromes: a prospective validation study.

Suspicion of myelodysplastic syndromes (MDS) is the most common reason for bone marrow aspirate in elderly patients. This study aimed to prospectively validate the accuracy for flow cytometric analysis of peripheral blood neutrophil myeloperoxidase expression in ruling out MDS. We enrolled 62 consecutive patients who were referred for suspected MDS, based on medical history and peripheral blood cytopenia. The accuracy of intra-individual robust coefficient of variation (RCV) for peripheral blood neutrophil myeloperoxidase expression was assessed with a prespecified 30% threshold. Cytomorphological evaluation of bone marrow aspirate performed by experienced hematopathologists confirmed MDS in 23 patients (prevalence, 37%), unconfirmed MDS in 32 patients (52%, including 3 patients with idiopathic cytopenia of undetermined significance (ICUS)), and was uninterpretable in 7 patients (11%). The median intra-individual RCV values for neutrophil myeloperoxidase expression in peripheral blood were 37.4% (range, 30.7-54.1), 29.2% (range, 28.1-32.1), and 29.1% (range, 24.7-37.8) for patients with confirmed suspicion of MDS, ICUS, and unconfirmed suspicion of MDS, respectively (P<0.001). The area under the ROC curve was 0.92 (95% confidence interval, 0.86-0.99). An intra-individual RCV value lower than 30% ruled out MDS for 35% (i.e., 19/55) patients referred for suspected disease, with 100% sensitivity (95% CI, 85-100%) and 100% negative predictive value (95% CI, 82-100%) estimates. This study shows that flow cytometric analysis of peripheral blood neutrophil myeloperoxidase expression might obviate the need for bone marrow aspirate for 35% of patients with suspected MDS. Trial registration: ClinicalTrials.gov identifier: NCT03363399 (first posted on December 6, 2017).