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).

Comparative diagnostic accuracy between simplified and original flow cytometric gating strategies for peripheral blood neutrophil myeloperoxidase expression in ruling out myelodysplastic syndromes.

BACKGROUND: Flow cytometric analysis of peripheral blood neutrophil myeloperoxidase expression is accurate in ruling out myelodyplastic syndromes (MDS) but might not be suitable for implementation in busy clinical laboratories. We aimed to simplify the original gating strategy and examine its accuracy. METHODS: Using the individual data from 62 consecutive participants enrolled in a prospective validation study, we assessed the agreement in intra-individual robust coefficient of variation (RCV) of peripheral blood neutrophil myeloperoxidase expression and compared diagnostic accuracy between the simplified and original gating strategies. RESULTS: Cytomorphological evaluation of bone marrow aspirate confirmed MDS in 23 patients (prevalence, 37%), unconfirmed MDS in 32 patients (52%), and was uninterpretable in 7 patients (11%). Median intra-individual RCV for simplified and original gating strategies were 30.7% (range, 24.7-54.4) and 30.6% (range, 24.7-54.1), with intra-class correlation coefficient quantifying absolute agreement equal to 1.00 (95% confidence interval [CI], 0.99 to 1.00). The areas under the receiver operating characteristic (ROC) curves were 0.93 (95% CI, 0.82-0.98) and 0.92 (95% CI, 0.82-0.98), respectively (P = .32). Using simplified or original gating strategy, intra-individual RCV values lower than a pre-specified threshold of 30.0% ruled out MDS for 35% (19 of 55) patients, with both sensitivity and negative predictive value estimates of 100%. CONCLUSIONS: The simplified gating strategy performs as well as the original one for ruling out MDS and has the potential to save time and reduce resource utilization. Yet, prospective validation of the simplified gating strategy is warranted before its adoption in routine. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03363399 (First posted on December 6, 2017).

Flow cytometry lyophilised-reagent tube for quantifying peripheral blood neutrophil myeloperoxidase expression in myelodysplastic syndromes (MPO-MDS-Develop): protocol for a diagnostic accuracy study.

INTRODUCTION: Suspicion of myelodysplastic syndromes (MDS) is the most common reason for bone marrow aspirate in elderly patients. Peripheral blood neutrophil myeloperoxidase expression quantified by flow cytometric analysis might rule out MDS for up to 35% of patients referred for suspected disease, without requiring bone marrow aspiration. Yet laboratory-developed liquid antibody cocktails have practical limitations, because of lack of standardisation and poor stability. This research project aims to estimate the level of agreement and comparative accuracy between a single-use flow cytometry tube of lyophilised reagents (BD Lyotube Stain 468) and its laboratory-developed liquid reagent counterpart in quantifying peripheral blood neutrophil myeloperoxidase expression, among adult patients referred for suspected MDS. METHODS AND ANALYSIS: The MPO-MDS-Develop project is a cross-sectional diagnostic accuracy study of two index tests by comparison with a reference standard in consecutive unselected adult patients conducted at a single university hospital. Flow cytometry analysis of peripheral blood samples will be performed by independent operators blinded to the reference diagnosis, using either Lyotube Stain 468 or laboratory-developed liquid reagent cocktail. The reference diagnosis of MDS will be established by cytomorphological evaluation of bone marrow aspirate by two independent haematopathologists blinded to the index test results. Morphologic assessment will be complemented by bone marrow flow cytometric score, karyotype and targeted next-generation sequencing panel of 43 genes, where relevant. The target sample size is 103 patients. ETHICS AND DISSEMINATION: An institutional review board (Comité de Protection des Personnes Sud Est III, Lyon, France) approved the protocol prior to study initiation (reference number: 2020-028-B). Participants will be recruited using an opt-out approach. Efforts will be made to release the primary results within 6 months of study completion. TRIAL REGISTRATION NUMBER: NCT04399018.