Flow cytometric detection of dyserythropoiesis: a sensitive and powerful diagnostic tool for myelodysplastic syndromes

Loss of hematopoietic progenitors heterogeneity is an adverse prognostic factor in lower-risk myelodysplastic neoplasms

Myelodysplastic neoplasms (MDS) are characterized by clonal evolution starting from the compartment of hematopoietic stem and progenitors cells (HSPCs), leading in some cases to leukemic transformation. We hypothesized that deciphering the diversity of the HSPCs compartment may allow for the early detection of an emergent sub-clone that drives disease progression. Deep analysis of HSPCs repartition by multiparametric flow cytometry revealed a strong disorder of the hematopoietic branching system in most patients at diagnosis with different phenotypic signatures closely related to specific MDS features. In two independent cohorts of 131 and 584 MDS, the HSPCs heterogeneity quantified through entropy calculation was decreased in 47% and 46% of cases, reflecting a more advanced state of the disease with deeper cytopenias, higher IPSS-R risk and accumulation of somatic mutations. We demonstrated that patients with lower-risk MDS and low CD34 + CD38+HSPCs entropy had an adverse outcome and that this parameter is as an independent predictive biomarker for progression free survival, leukemia free survival and overall survival. Analysis of HSPCs repartition at diagnosis represents therefore a very powerful tool to identify lower-risk MDS patients with a worse outcome and valuable for clinical decision-making, which could be fully integrated in the MDS diagnostic workflow.

Flow Cytometric Assessment of Myelodysplastic Syndromes/Neoplasms

Myelodysplastic syndromes/neoplasms (MDS) are a heterogeneous class of hematopoietic stem cell neoplasms characterized by ineffective hematopoiesis leading to peripheral cytopenias. This group of diseases is typically diagnosed using a combination of clinical, morphologic, and genetic criteria. Many studies have described the value of multiparametric flow cytometry (MFC) in the diagnosis, classification, and prognostication of MDS. This review summarizes the approach to MDS diagnosis and immunophenotypic characterization using MFC and describes the current state while highlighting future opportunities and potential pitfalls.

ProGraME: A novel flow cytometry algorithm for the diagnosis of low-risk myelodysplastic syndromes in patients with cytopenia

OBJECTIVES

Flow cytometry (FC) is, together with morphology, genetics, and cytogenetics, used in the diagnostic assessment of cytopenia, as its value in evaluating bone marrow dysplasia been highlighted by several studies. However, despite the development of algorithms and guidelines, there is still a lack of standardization of the FC assessment of bone marrow dysplasia.

METHODS

By combining FC, together with morphological analysis and cytogenetic/molecular assessment in a training cohort of 209 patients, we created a novel score, ProGraME, which includes four parameters, each from a different cell lineage (Progenitor cells, Granulocytes, Monocytes, Erythroid precursors), solely based on relevant population gating. Points for ProGraME were attained for: lymphoid precursors ≤5% of all CD34+ cells (1.5 point); a granulocyte-to-lymphocyte side-scatter ratio ≤6 (1 point); a monocyte CD33-CV% ≥ 63 (2 points), and an erythroid precursor CD36-CV% ≥ 65 (2 points).

RESULTS

Using a cutoff of ≥2 as suggestive of dysplasia, ProGraME showed a sensitivity of 91% and a specificity of 81% in the training cohort and 95% and 75%, respectively, in an independent validation cohort of 159 patients. In addition, ProGraME had a very high negative predictive value of 97.1% and 97.8% in the training and validation cohorts, respectively, offering a useful tool for excluding bone marrow dysplasia. Finally, among the 23 CCUS patients that scored positive for dysplasia with ProGraME in the training cohort, 16 of them (69%) carried high-risk mutations, suggesting that FC might help identify early changes of dysplasia.

CONCLUSIONS

ProGraME can potentially optimize the FC diagnosis of low-risk myelodysplasia without minimal requirements of flow analysis other than accurate population gating.

[Treatment of lower risk myelodysplastic syndromes]

For low-risk myelodysplastic syndromes, the goal of treatment is to correct cytopenias or their consequences. Erythropoiesis-stimulating agents have an important role in the management of anemia. In this chapter, we will detail the response to ESAs, the factors predictive of response to ESAs. However, the search for new therapeutic options for low-risk, ESA-resistant MDS remains necessary as the incidence of AML transformation of the patients is higher. We can retain luspatercept for MDS with excess ring of sideroblasts, lenalidomide, and some molecules currently being tested such as imetelstat or roxedustat. However, the search for new therapeutic options for ESA-resistant low-risk MDS remains necessary. We can use androgenotherapy or TPO agonists in limited access for symptomatic thrombocytopenia.

Deep immunophenotypic analysis of the bone marrow progenitor cells in myelodysplastic syndromes

BACKGROUND

Diagnosis of myelodysplastic syndromes (MDS) is often challenging and requires integration of clinical, morphologic, cytogenetics and molecular information. Flow cytometry immunophenotyping (FCIP) can support the diagnosis by demonstration of numerical and immunophenotypic abnormalities of progenitor and maturing myelomonocytic and erythroid populations. We have previously shown that comprehensive immunophenotypic analysis of the progenitor population is valuable in the diagnosis of MDS and myelodysplastic/myeloproliferative neoplasms (MDS/MPN). This study was designed to improve the analysis method and confirm its value in a larger cohort of patients.

METHODS

FCIP of bone marrow samples from 105 patients with cytopenia(s) (with or without leukocytosis) and clinical concern for MDS or MDS/MPN was performed using a single-tube/10-color/13-marker assay. A modified analysis approach was used to obtain 11 progenitor parameters and 2 myelomonocytic parameters.

RESULTS

Significantly higher number of abnormalities were identified in MDS and MDS/MPN cases when compared to cytopenic patients not meeting the diagnostic criteria for MDS (Non-MDS). A FCIP score that combined the 13 parameters showed a sensitivity of 89.8% and specificity of 93.5% for the diagnosis of MDS and MDS/MPN. The sensitivity was 100% for both MDS/MPN and higher-risk MDS, and 81.3% for lower-risk MDS.

CONCLUSION

This study confirms that detailed immunophenotypic analysis of the progenitor population is powerful in the diagnosis of MDS and MDS/MPN. The combination of markers used in the panel allowed for evaluation of two relatively new parameters, namely myeloid progenitor heterogeneity and stem cell aberrancy, which improved the sensitivity of the assay for lower-risk MDS.

CAR virus receptor mediates erythroid differentiation and migration and is downregulated in MDS

Myelodysplastic syndromes (MDS) are myeloid neoplasms presenting with dysplasia in the bone marrow (BM) and peripheral cytopenia. In most patients anemia develops. We screened for genes that are expressed abnormally in erythroid progenitor cells (EP) and contribute to the pathogenesis of MDS. We found that the Coxsackie-Adenovirus receptor (CAR = CXADR) is markedly downregulated in CD45low/CD105+ EP in MDS patients compared to control EP. Correspondingly, the erythroblast cell lines HEL, K562, and KU812 stained negative for CAR. Lentiviral transduction of the full-length CXADR gene into these cells resulted in an increased expression of early erythroid antigens, including CD36, CD71, and glycophorin A. In addition, CXADR-transduction resulted in an increased migration against a serum protein gradient, whereas truncated CXADR variants did not induce expression of erythroid antigens or migration. Furthermore, conditional knock-out of Cxadr in C57BL/6 mice resulted in anemia and erythroid dysplasia. Finally, decreased CAR expression on EP was found to correlate with high-risk MDS and decreased survival. Together, CAR is a functionally relevant marker that is down-regulated on EP in MDS and is of prognostic significance. Decreased CAR expression may contribute to the maturation defect and altered migration of EP and thus their pathologic accumulation in the BM in MDS.

Reliability of flow-cytometry in diagnosis and prognostic stratification of myelodysplastic syndromes: correlations with morphology and mutational profile

Diagnosis and prognostic stratification of myelodysplastic syndromes (MDS) have been complemented by new techniques, including flow cytometry and NGS. To analyze the relationship between molecular and cytofluorimetric data, we enrolled in this retrospective study, 145 patients, including 106 diagnosed with MDS and 39 controls. At disease onset, immunophenotypic (IF), cytogenetic tests, and cytomorphological (CM) examination on bone marrow were carried out in all patients, while NGS was performed in 58 cases. Ogata score presented a specificity of 100% and a sensitivity of 59%. The detection of at least two phenotypic aberrancies in Ogata negative patients increased the sensitivity to 83% and specificity to 87%. Correlations were identified between IF aberrancies and mutations, including positive Ogata>2 and mutations in SRSF2 (p=0.035), CD15 and U2AF1 (0.032), CD56 and DNMT3A (p=0.042), and CD38 and TP53 (p=0.026). In multivariate analysis, U2AF1 mutations, associated with del(20q) and/or abnormalities of chromosome 7 (group 4 as defined by the EuroMDS score), significantly correlated with an inferior overall survival (p=0.019). These parameters and Ogata score>2 also showed a significant correlation with inferior event-free survival (p=0.023 and p=0.041, respectively). Both CM and FC features correlated with prognosis and mutational patterns. In an integrated MDS work-up, these tools may guide indications for mutational screening for optimal risk stratification.

[MDS & CMML: Diagnostic and classification]

In 2023, a diagnosis process of myelodysplastic syndrome (MDS) or chronic myelomonocytic leukemia (CMML) is mainly based on morphological results obtained on bone marrow and blood smears which could be completed by cytogenetical analyses. Due to recent finding, flow cytometry data are recognized as useful for the diagnosis of CMML especially. Actual classifications and prognostic scoring systems have changed and nowadays include results of high-throughput sequencing approaches in addition to cytogenetical results. All together, these data allow the medical world to correctly evaluate the prognosis of these patients and to provide some information for targeted therapies. This chapter will provide the most important modifications recently published in the field of diagnosis and prognosis of MDS and CMML.

Clinical Flow Cytometry Analysis in the Setting of Chronic Myeloid Neoplasms and Clonal Hematopoiesis

The utility of flow cytometry analysis in the evaluation of chronic myeloid neoplasms, such as myelodysplastic neoplasms and chronic myeloproliferative neoplasms, continues to be emphasized and explored. Recently flow cytometry analysis has been also proven to be able to distinguish persistent clonal hematopoiesis from measurable residual disease in patients with acute myeloid leukemia (AML), a finding with potential critical treatment impact in the management of patients with AML.

Diagnosis of erythroid dysplasia by flow cytometry: a review

INTRODUCTION

The diagnosis of myelodysplastic syndrome (MDS) is complex. Flow cytometric analysis of the myelomonocytic compartment can be helpful, but it is highly subjective and reproducibility by non-specialized groups is unclear. Analysis of the erythroid lineage by flow cytometry is emerging as potentially more reproducible and easier to conduct, while keeping a high diagnostic performance.

AREAS COVERED

We review the evidence in this area, including 1) the use of well-established markers - CD71 and CD36 - and other less well-established markers and parameters; 2) the use of flow cytometric scores for the erythroid lineage; and 3) additional aspects, including the emergence of computational tools and the roles of flow cytometry beyond diagnosis. Finally, we discuss the limitations with the current evidence, including 1) the impact of the sample processing protocol and reagents on the results, 2) the lack of a standard gating strategy, and 3) conceptualization and design issues in the available publications.

EXPERT OPINION

We end by offering our recommendations for the current use - and our personal take on the value - of the analysis of erythroid lineage by flow cytometry.

CD36 relative mean fluorescence intensity of CD105+ nucleated erythroid cells can be used to differentiate myelodysplastic syndrome from megaloblastic anemia

This study aims to evaluate the differences in CD105⁺ nucleated erythroid cell (NEC) immunophenotypes between myelodysplastic syndrome (MDS) and megaloblastic anemia (MA) using multiparameter flow cytometry and to screen potential markers. We analyzed bone marrow sample data from 37 patients with MDS, 35 with MA, 53 with iron-deficiency anemia (anemic controls), and 35 without anemia (normal controls). Compared with normal controls, the MDS and MA groups showed a decrease in the proportion of CD117⁺CD105⁺NEC and the relative mean fluorescence intensity (RMFI) of CD71 in CD105⁺NEC, accompanied by an increase in the coefficient of variation (CV) of CD71 and CD36. Additionally, CD36 RMFI of CD105⁺NEC increased in the MA group. Compared with anemia controls, the MDS and MA groups showed a significant increase in CD36 CV of CD105⁺NEC, and the CD36 RMFI in the MA group increased while that in the MDS group decreased. The proportions of CD117⁺CD105⁺NEC, CD36 CV, and CD36 RMFI in CD105⁺NEC differed significantly between MDS and MA groups. Among them, CD36 RMFI had good diagnostic performance (area under the curve: 0.844, 95% confidence interval: 0.753-0.935). CD36 RMFI of CD105⁺NEC may be a helpful marker in differentiating MDS and MA using multiparameter flow cytometry.

Comparison of five diagnostic flow cytometry scores in patients with myelodysplastic syndromes: Diagnostic power and prognostic impact

BACKGROUND

Flow cytometry (FCM) is a co-criterion in myelodysplastic syndromes (MDS) diagnostics according to the WHO classification. The presented study compared diagnostic power and prognostic impact of different FCM-based scores.

METHODS

A total of 807 bone marrow (BM) samples of patients with cytopenia (543 MDS, 153 non-clonal cytopenias, 111 non-MDS myeloid malignancies) and 78 healthy controls have been investigated using a standardized 8-color-FCM procedure. FCSS, Ogata-score, iFS, RED-score, and ELN-NEC were analyzed for sensitivity and specificity in comparison to standard diagnostic tools. Median follow up for patients was 26 month (range: 0.2-89).

RESULTS

The iFS showed the highest accuracy (80%) with the best balance between sensitivity (79%) and specificity (86%). This was also valid in MDS with very low IPSS-R and even in MDS without ring sideroblasts, with normal blast count and karyotype, where iFS could confirm diagnosis in 62% and 65% of patients. Besides the high diagnostic power, the established iFS category "consistent with MDS" was associated with inferior overall survival (OS) independent from WHO classification (median: 51 month vs. not reached, p < 0.0001). Remarkably, this iFS category redefined a subgroup of patients with worse OS within IPSS-R low-risk category (73 month vs. not reached, p = 0.0433). Finally, multivariable analysis showed that iFS added independent prognostic information regarding OS besides IPSS-R.

CONCLUSIONS

The iFS separates non-clonal cytopenias and MDS with the highest accuracy, provided information in addition to standard diagnostic procedures, and refined established prognostic tools for outcome prediction.

Erythroid side scatter: A parameter that improves diagnostic accuracy of flow cytometry myelodysplastic syndrome scoring

BACKGROUND

Flow cytometry immunophenotyping (FCM) is a benchmark test for integrated diagnosis of myelodysplastic syndromes (MDS). Our department's FCM-MDS-score follows international guidelines and additionally includes the maturing erythroid (mEry) side scatter (SSC)/lymphocyte SSC ratio (mErySSCr), often increased in MDS patients. A recent exploratory computational flow analysis study highlighted mErySSC as the top feature for separating MDS from non-MDS. Thus, we sought to systematically evaluate the diagnostic accuracy of mErySSCr in conventional diagnostic FCM as used currently in-house.

METHODS

Historical MDS (n = 93), chronic myelomonocytic leukemia (CMML; n = 27) and non-neoplastic cytopenia (n = 57) cohorts were created. Differences between these cohorts and LG-MDS entities were mapped and the mErySSCr cut-off was refined. Prospective bone marrows (n = 213) received for marrow failure work-up were used to determine the sensitivity and specificity of mErySSCr, both as a sole parameter and as a component of the MDS-score.

RESULTS

Low-grade (LG)-MDS mErySSCr differed more prominently from controls (p = <0.0001) than high-grade (HG)-MDS (p = 0.024). CMML and controls had a similar mErySSCr. As sole parameter, mErySSCr specificity was 91.1% (n = 112 non-MDS diagnoses) and sensitivity was 36% for LG-MDS (n = 36) and 25% for new HG-MDS diagnoses (n = 16). The specificity of the MDS-score was similar if mErySSCr was omitted (81.3% with and 82.1% without). The MDS-score sensitivity for new HG-MDS diagnoses and CMML (n = 17) was 100%, and was not affected by mErySSCr. The score sensitivity for LG-MDS however, dropped from 86.1% to 72.2% when mErySSCr was excluded.

CONCLUSION

mErySSCr increases the diagnostic accuracy of flow-based MDS scoring in our setting, particularly for LG-MDS.

Multiparameter flow cytometry in the evaluation of myelodysplasia: Analytical issues: Recommendations from the European LeukemiaNet/International Myelodysplastic Syndrome Flow Cytometry Working Group

Multiparameter flow cytometry (MFC) is one of the essential ancillary methods in bone marrow (BM) investigation of patients with cytopenia and suspected myelodysplastic syndrome (MDS). MFC can also be applied in the follow-up of MDS patients undergoing treatment. This document summarizes recommendations from the International/European Leukemia Net Working Group for Flow Cytometry in Myelodysplastic Syndromes (ELN iMDS Flow) on the analytical issues in MFC for the diagnostic work-up of MDS. Recommendations for the analysis of several BM cell subsets such as myeloid precursors, maturing granulocytic and monocytic components and erythropoiesis are given. A core set of 17 markers identified as independently related to a cytomorphologic diagnosis of myelodysplasia is suggested as mandatory for MFC evaluation of BM in a patient with cytopenia. A myeloid precursor cell (CD34⁺ CD19^- ) count >3% should be considered immunophenotypically indicative of myelodysplasia. However, MFC results should always be evaluated as part of an integrated hematopathology work-up. Looking forward, several machine-learning-based analytical tools of interest should be applied in parallel to conventional analytical methods to investigate their usefulness in integrated diagnostics, risk stratification, and potentially even in the evaluation of response to therapy, based on MFC data. In addition, compiling large uniform datasets is desirable, as most of the machine-learning-based methods tend to perform better with larger numbers of investigated samples, especially in such a heterogeneous disease as MDS.

Clinical application of flow cytometry in patients with unexplained cytopenia and suspected myelodysplastic syndrome: A report of the European LeukemiaNet International MDS-Flow Cytometry Working Group

This article discusses the rationale for inclusion of flow cytometry (FCM) in the diagnostic investigation and evaluation of cytopenias of uncertain origin and suspected myelodysplastic syndromes (MDS) by the European LeukemiaNet international MDS Flow Working Group (ELN iMDS Flow WG). The WHO 2016 classification recognizes that FCM contributes to the diagnosis of MDS and may be useful for prognostication, prediction, and evaluation of response to therapy and follow-up of MDS patients.

Flow cytometric analysis of myelodysplasia: Pre-analytical and technical issues-Recommendations from the European LeukemiaNet

BACKGROUND

Flow cytometry (FCM) aids the diagnosis and prognostic stratification of patients with suspected or confirmed myelodysplastic syndrome (MDS). Over the past few years, significant progress has been made in the FCM field concerning technical issues (including software and hardware) and pre-analytical procedures.

METHODS

Recommendations are made based on the data and expert discussions generated from 13 yearly meetings of the European LeukemiaNet international MDS Flow working group.

RESULTS

We report here on the experiences and recommendations concerning (1) the optimal methods of sample processing and handling, (2) antibody panels and fluorochromes, and (3) current hardware technologies.

CONCLUSIONS

These recommendations will support and facilitate the appropriate application of FCM assays in the diagnostic workup of MDS patients. Further standardization and harmonization will be required to integrate FCM in MDS diagnostic evaluations in daily practice.

Abnormal CD13/HLA-DR Expression Pattern on Myeloblasts Predicts Development of Myeloid Neoplasia in Patients With Clonal Cytopenia of Undetermined Significance

OBJECTIVES

Patients with clonal cytopenia of undetermined significance (CCUS) are at increased risk of developing myeloid neoplasia (MN). We evaluated whether a simple flow cytometry immunophenotyping (FCIP) assay could differentiate the risk of development of MN in patients with CCUS.

METHODS

Bone marrow aspirates were assessed by FCIP panel in a cohort of 80 patients identified as having CCUS based on next-generation sequencing or cytogenetics from March 2015 to May 2020, with available samples. Flow cytometric assay included CD13/HLA-DR expression pattern on CD34-positive myeloblasts; CD13/CD16 pattern on maturing granulocytic precursors; and aberrant expression of CD2, CD7, or CD56 on CD34-positive myeloblasts. Relevant demographic, comorbidity, and clinical and laboratory data, including the type and extent of genetic abnormalities, were extracted from the electronic health record.

RESULTS

In total, 17 (21%) patients with CCUS developed MN over the follow-up period (median survival follow-up, 28 months [95% confidence interval, 19-31]). Flow cytometry immunophenotyping abnormalities, including the aberrant pattern of CD13/HLA-DR expression, as detected at the time of the diagnosis of CCUS, were significantly associated with risk of developing MN (hazard ratio, 2.97; P = .006). Additional FCIP parameters associated with the development of MN included abnormal expression of CD7 on myeloblasts and the presence vs absence of any FCIP abnormality.

CONCLUSIONS

A simple FCIP approach that includes assessment of CD13/HLA-DR pattern on CD34-positive myeloblasts can be useful in identifying patients with CCUS at higher risk of developing MN.

Diagnosis of Myelodysplastic Syndromes: From Immunological Observations to Clinical Applications

Myelodysplastic syndromes (MDS) constitute a very heterogeneous group of diseases with a high prevalence in elderly patients and a propensity for progression to acute myeloid leukemia. The complexity of these hematopoietic malignancies is revealed by the multiple recurrent somatic mutations involved in MDS pathogenesis and the paradoxical common phenotype observed in these patients characterized by ineffective hematopoiesis and cytopenia. In the context of population aging, the incidence of MDS will strongly increase in the future. Thus, precise diagnosis and evaluation of the progression risk of these diseases are imperative to adapt the treatment. Dysregulations of both innate and adaptive immune systems are frequently detected in MDS patients, and their critical role in MDS pathogenesis is now commonly accepted. However, different immune dysregulations and/or dysfunctions can be dynamically observed during the course of the disease. Monitoring the immune system therefore represents a new attractive tool for a more precise characterization of MDS at diagnosis and for identifying patients who may benefit from immunotherapy. We review here the current knowledge of the critical role of immune dysfunctions in both MDS and MDS precursor conditions and discuss the opportunities offered by the detection of these dysregulations for patient stratification.

Unsupervised cluster analysis and subset characterization of abnormal erythropoiesis using the bioinformatic Flow-Self Organizing Maps algorithm

Background

The Flow‐Self Organizing Maps (FlowSOM) artificial intelligence (AI) program, available within the Bioconductor open‐source R‐project, allows for an unsupervised visualization and interpretation of multiparameter flow cytometry (MFC) data.

Methods

Applied to a reference merged file from 11 normal bone marrows (BM) analyzed with an MFC panel targeting erythropoiesis, FlowSOM allowed to identify six subpopulations of erythropoietic precursors (EPs). In order to find out how this program would help in the characterization of abnormalities in erythropoiesis, MFC data from list‐mode files of 16 patients (5 with non‐clonal anemia and 11 with myelodysplastic syndrome [MDS] at diagnosis) were analyzed.

Results

Unsupervised FlowSOM analysis identified 18 additional subsets of EPs not present in the merged normal BM samples. Most of them involved subtle unexpected and previously unreported modifications in CD36 and/or CD71 antigen expression and in side scatter characteristics. Three patterns were observed in MDS patient samples: i) EPs with decreased proliferation and abnormal proliferating precursors, ii) EPs with a normal proliferating fraction and maturation defects in late precursors, and iii) EPs with a reduced erythropoietic fraction but mostly normal patterns suggesting that erythropoiesis was less affected. Additionally, analysis of sequential samples from an MDS patient under treatment showed a decrease of abnormal subsets after azacytidine treatment and near normalization after allogeneic hematopoietic stem‐cell transplantation.

Conclusion

Unsupervised clustering analysis of MFC data discloses subtle alterations in erythropoiesis not detectable by cytology nor FCM supervised analysis. This novel AI analytical approach sheds some new light on the pathophysiology of these conditions.

Comparison of flow cytometry with other modalities in the diagnosis of myelodysplastic syndrome

INTRODUCTION

The myelodysplastic syndromes (MDSs) are heterogeneous myeloid malignancies, conventionally diagnosed by cytomorphology and cytogenetics, with an emerging role for flow cytometry. This study compared the performance of a 4-parameter flow cytometry scoring system, the Ogata Score, with other modalities in the diagnosis of MDS.

METHODS

Bone marrow aspirate and trephine biopsies from 238 patients performed to assess for possible MDS were analysed, and the flow cytometry score was retrospectively applied. The sensitivity and specificity of the flow cytometry score, the aspirate microscopy, the trephine microscopy with immunohistochemistry, and cytogenetic and molecular results were determined relative to the final diagnosis.

RESULTS

The medical records of the 238 patients were reviewed to determine the final clinical diagnosis made at the time of the bone marrow examination. This final diagnosis of MDS, possible MDS or not MDS, was based on clinical features and laboratory tests, including all parameters of the bone marrow investigation, except for the flow cytometry score, which was only determined for this study. The flow cytometry score was 67.4% sensitive and 93.8% specific. Aspirate microscopy had higher sensitivity (83.7%) and similar specificity (92.0%), whereas trephine microscopy had similar sensitivity (66.3%) and specificity (89.4%) to flow cytometry. Although the flow cytometry score had a lower sensitivity than aspirate microscopy, in 18 patients (7.6% of the total) the flow cytometry score was positive for MDS, whereas aspirate microscopy was negative or inconclusive.

CONCLUSION

The flow cytometry score and trephine microscopy exhibited reasonable sensitivity and high specificity, and complement aspirate microscopy in the assessment of MDS.

Efficacy and safety of ruxolitinib in ineffective erythropoiesis suppression as a pretransplantation treatment for pediatric patients with beta-thalassemia major

BACKGROUND

Ineffective erythropoiesis (IE) is the most prominent feature of transfusion-dependent beta-thalassemia (TDT), which leads to extramedullary hemopoiesis. The rejection rate in allogeneic hematopoietic stem cell transplantation (HSCT) is high in heavily transfused patients with TDT accompanied by prominent IE. Therefore, a pretransplantation treatment bridging to HSCT is often used to reduce allosensitization and IE. Ruxolitinib is a JAK-1/JAK-2 inhibitor and has showed its efficacy in suppressing IE and the immune system. A previously published study on RUX in adult patients with TDT has revealed that this treatment significantly reduces spleen size and is well tolerated.

PROCEDURE

Ten patients (5-14 years old) with TDT and an enlarged spleen were enrolled. The dose of ruxolitinib was adjusted for age: for patients <11 years: 40-100 mg/m² total daily dose and for patients >11 years: 20-30 mg/m² total daily dose. HSCT was performed in 8 of 10 patients.

RESULTS

After the first 3 months of ruxolitinib therapy, spleen volume decreased in 9 of 10 cases by 9.1%-67.5% (M = 35.4%) compared with the initial size (P = 0.003). The adverse events of ruxolitinib (infectious complications, moderate thrombocytopenia, and headache) were successfully managed by reducing the dose. The outcomes of HSCT were favorable in seven of eight cases.

CONCLUSION

Ruxolitinib is promising as a short-term pre-HSCT treatment for pediatric patients with TDT and pronounced IE.

Computational flow cytometry as a diagnostic tool in suspected-myelodysplastic syndromes

The diagnostic work‐up of patients suspected for myelodysplastic syndromes is challenging and mainly relies on bone marrow morphology and cytogenetics. In this study, we developed and prospectively validated a fully computational tool for flow cytometry diagnostics in suspected‐MDS. The computational diagnostic workflow consists of methods for pre‐processing flow cytometry data, followed by a cell population detection method (FlowSOM) and a machine learning classifier (Random Forest). Based on a six tubes FC panel, the workflow obtained a 90% sensitivity and 93% specificity in an independent validation cohort. For practical advantages (e.g., reduced processing time and costs), a second computational diagnostic workflow was trained, solely based on the best performing single tube of the training cohort. This workflow obtained 97% sensitivity and 95% specificity in the prospective validation cohort. Both workflows outperformed the conventional, expert analyzed flow cytometry scores for diagnosis with respect to accuracy, objectivity and time investment (less than 2 min per patient).

Distinct bone marrow immunophenotypic features define the splicing factor 3B subunit 1 (SF3B1)-mutant myelodysplastic syndromes subtype

Splicing factor 3B subunit 1 (SF3B1) mutations define a distinct myelodysplastic syndromes (MDS) patient group with a relatively favourable disease course and high response rates to luspatercept. Few data are available on bone marrow phenotype beyond ring sideroblasts in this subgroup of patients with MDS. In the present study, we identified immunophenotypic erythroid, myelomonocyte and progenitor features associated with SF3B1 mutations. In addition, we illustrate that SF3B1-mutation type is associated with distinct immunophenotypic features, and show the impact of co-occurrence of a SF3B1 mutation and a deletion of chromosome 5q on bone marrow immunophenotype. These genotype-phenotype associations and phenotypic subtypes within SF3B1-MDS provide leads that may further refine prognostication and therapeutic strategies for this particular MDS subgroup.

Exploring dyserythropoiesis in patients with myelodysplastic syndrome by imaging flow cytometry and machine-learning assisted morphometrics

BACKGROUND

The hallmark of myelodysplastic syndrome (MDS) remains dysplasia in the bone marrow (BM). However, diagnosing MDS may be challenging and subject to inter-observer variability. Thus, there is an unmet need for novel objective, standardized and reproducible methods for evaluating dysplasia. Imaging flow cytometry (IFC) offers combined analyses of phenotypic and image-based morphometric parameters, for example, cell size and nuclearity. Hence, we hypothesized IFC to be a useful tool in MDS diagnostics.

METHODS

Using a different-from-normal approach, we investigated dyserythropoiesis by quantifying morphometric features in a median of 5953 erythroblasts (range: 489-68,503) from 14 MDS patients, 11 healthy donors, 6 non-MDS controls with increased erythropoiesis, and 6 patients with cytopenia.

RESULTS

First, we morphometrically confirmed normal erythroid maturation, as immunophenotypically defined erythroid precursors could be sequenced by significantly decreasing cell-, nuclear- and cytoplasm area. In MDS samples, we demonstrated cell size enlargement and increased fractions of macronormoblasts in late-stage erythroblasts (both p < .0001). Interestingly, cytopenic controls with high-risk mutational patterns displayed highly aberrant cell size morphometrics. Furthermore, assisted by machine learning algorithms, we reliably identified and enumerated true binucleated erythroblasts at a significantly higher frequency in two out of three erythroblast maturation stages in MDS patients compared to normal BM (both p = .0001).

CONCLUSION

We demonstrate proof-of-concept results of the applicability of automated IFC-based techniques to study and quantify morphometric changes in dyserythropoietic BM cells. We propose that IFC holds great promise as a powerful and objective tool in the complex setting of MDS diagnostics with the potential for minimizing inter-observer variability.

Diagnostic significance of flow cytometry scales in diagnostics of myelodysplastic syndromes

BACKGROUND

Myelodysplastic syndromes (MDS) can present a challenge for clinicians. Multicolor flow cytometry (MFC) can aid in establishing a diagnosis. The aim of this study was to determine the optimal MFC approach for MDS.

METHODS

The study included 102 MDS (39 low-grade MDS), 83 cytopenic patients without myeloid neoplastic disorders (control group), and 35 healthy donors. Bone marrow was analyzed using a six-color MFC. Analysis was conducted according to the "Ogata score," "Wells score," and the integrated flow cytometry (iFC) score.

RESULTS

The respective sensitivity and specificity values were 77.5% and 90.4% for the Ogata score, 79.4% and 81.9% for the Wells score, and 87.3% and 87.6% for the iFC score. Specificity was not 100% due to deviations of MFC parameters in the control group. Patients with paroxysmal nocturnal hemoglobinuria (PNH) had higher levels of CD34⁺ CD7⁺ myeloid cells than donors. Aplastic anemia and PNH were characterized by a high proportion of CD56⁺ cells among CD34⁺ precursors and neutrophils. The proportion of MDS-related features increased with the progression of MDS. The highest number of CD34⁺ blasts was found in MDS with excess blasts. MDS with isolated del(5q) was characterized by a high proportion of CD34⁺ CD7⁺ cells and low granularity of neutrophils. In 39 low-grade MDS, the sensitivities were 53.8%, 61.5%, and 71.8% for Ogata score, Wells score, and iFC, respectively.

CONCLUSION

The results support iFC as a useful diagnostic tool in MDS.

The diagnostic and prognostic role of flow cytometry in idiopathic and clonal cytopenia of undetermined significance (ICUS/CCUS): A single-center analysis of 79 patients

OBJECTIVE

The aim of this study was to evaluate the diagnostic and prognostic role of multiparameter flow cytometry (FC) in patients with idiopathic cytopenia of undetermined significance (ICUS) and clonal cytopenia of undetermined significance (CCUS).

METHODS

We performed FC using a standardized panel and two different diagnostic algorithms (Ogata, Wells) in a well-characterized cohort of 79 patients with ICUS/CCUS and compared it with a retrospective blinded morphological evaluation and data from targeted next-generation DNA sequencing of 20 myelodysplastic syndrome (MDS)-related genes.

RESULTS

Our data show that FC has low sensitivity in distinguishing CCUS from ICUS patients (40.5% for Ogata score and 59.5% for Wells score). The Wells score was suggestive of dysplasia in ICUS/CCUS patients with concurrent morphological signs of dysplasia in the bone marrow (following re-evaluation by two hematopathologists) and in CCUS patients with a higher mutational burden. Eight patients with ICUS/CCUS from our cohort progressed to another myeloid malignancy (MDS, acute myeloid leukemia, or chronic myelomonocytic leukemia), all showing flow cytometric signs of dysplasia.

CONCLUSION

FC performs poorly in diagnosing CCUS versus ICUS. However, it can potentially provide prognostic information in cytopenic patients by identifying a subgroup of patients with a higher grade of dysplasia, higher mutational burden, and higher risk of progression and, together with mutational screening, also identify a group of patients who might require morphological reassessment of dysplastic changes in their bone marrow.

CD177 Enhances the Detection of Myelodysplastic Syndrome by Flow Cytometry

OBJECTIVES

Previously we demonstrated that a decreased percentage of CD177-positive granulocytes detected by flow cytometry (FCM) was associated with myelodysplastic syndrome (MDS). Here we expand on those findings to more rigorously evaluate the utility of CD177 for the detection of MDS.

METHODS

Two hundred patient samples (100 MDS and 100 controls) were evaluated for granulocyte expression of CD177 and 11 other flow cytometric parameters known to be associated with MDS.

RESULTS

We show that CD177, as a single analyte, is highly correlated with MDS with a receiver operating characteristic area under curve value of 0.8. CD177 expression below 30% demonstrated a sensitivity of 51% and a specificity of 94% for detecting MDS with a positive predictive value of 89.5%. In multivariate analysis of 12 MDS-associated FCM metrics, CD177 and the Ogata parameters were significant indicators of MDS, and CD177 increased sensitivity of the Ogata score by 16% (63%-79%) for predicting MDS. Finally, diagnostic criteria incorporating these parameters with a 1% blast cutoff level and CD177 resulted in a sensitivity of 90% and specificity of 91% for detecting MDS.

CONCLUSIONS

The findings indicate CD177 is a useful FCM marker for MDS.

Myelodysplastic syndrome: validation of flow cytometry multilineage score system

OBJECTIVE

To validate multilineage score system correlating results of flow cytometry, cytogenetics, cytomorphology and histology from samples of patients with suspected myelodysplastic syndrome or cytopenia of unknown origin.

METHODS

A retrospective study analyzing laboratory data of 49 patients with suspected myelodysplastic syndrome or cytopenia of unknown origin, carried out between May and September 2017. The inclusion criteria were availability of flow cytometry results, and at least one more method, such as morphology, histology or cytogenetics. Thirty-eight patients were classified as diagnosis of myelodysplastic syndromes, whereas 11 were classified as normal. Patients were evaluated based on score systems, Ogata score and flow cytometry multilineage score.

RESULTS

Comparing the scores obtained in the Ogata score and the multilineage score, it was observed that in four cases the Ogata score was zero or 1 point, while the multilineage score was higher than 3 points. In addition, in 12 cases with Ogata score of 2, the multilineage score was greater than 3.

CONCLUSION

The flow cytometry multilineage score system demonstrated to be more effective in dysplasia analysis, by assessing the erythroid, monocytic, granulocytic and precursor cell lineages, apart from the parameters evaluated by the Ogata score.

Myelodysplastic Syndromes: Laboratory Workup in the Context of New Concepts and Classification Criteria

PURPOSE OF REVIEW

This review provides a comprehensive update of myelodysplastic syndromes (MDS) and their diagnostic criteria, with emphasis on novel concepts and state-of-the-art laboratory workup, including multiparameter/multicolor flow cytometry, chromosome analysis, and mutation profiling.

RECENT FINDINGS

Recent advances in genetics and molecular technologies have provided unprecedented insights into the pathogenic mechanisms and genomic landscape of MDS and its precursor lesions. This has resulted in revised diagnostic criteria in the World Health Organization (WHO) classification and proposed new terminology for early lesions such as clonal hematopoiesis of indeterminate potential (CHIP). Against this landscape, a thorough understanding of the advantages and limitations of laboratory tests employed in the evaluation of patients with cytopenia has gained unprecedented importance. Healthcare providers involved in the care of patients with hematologic diseases should be aware of the intricacies of laboratory workup of such patients, particularly in view of the novel concepts and classification criteria of MDS.

"Bone marrow aspirate automated counts on hematology analyzers: formulating a scoring system based on hematology parameters, to discriminate reactive versus myelodysplastic syndrome-related bone marrows"

INTRODUCTION

Diagnosis of myelodysplastic syndromes (MDS) is usually challenging. In this context, we have attempted to employ data derived from automated analysis of bone marrow (BM) samples as an ancillary tool for the discrimination between reactive marrow and MDS.

METHODS

A total of 101 BM anticoagulated samples referred for flow cytometry (FCM) analysis on the clinical suspicion of MDS had been previously counted in a Mindray BC-6800 hematology analyzer (testing set). Among them, 22/101 randomly selected BM samples (comparison set) had been also simultaneously counted by an Advia 2120 and a CELL-DYN Sapphire hematology analyzer. Selected parameters obtained by Mindray BC-6800 were retrospectively evaluated with ROC and regression analysis in an attempt to formulate a discriminative scoring system (SS) for MDS. This system was further evaluated in the comparison set.

RESULTS

The diagnosis of MDS was established in 37/101 patients assessed ("MDS" group). Three patients were diagnosed with myelodysplastic/myeloproliferative neoplasm (MDS/MPN), while 61 revealed a "reactive" bone marrow ("RBM" group). Statistical analysis revealed significant differences in Hb, RDW-CV%, NRBC%, and RET% values between the "MDS" and the "RBM" group. Specific cutoff values were then indicated and employed for the formulation of a SS of high sensitivity (86.84%) and specificity (86.89%). The encouraging performance characteristics of the proposed SS were also confirmed in the BM comparison set.

CONCLUSION

Automated BM counts on hematology analyzers contributed to the formulation of a SS for the screening discrimination between reactive and MDS BM fluids, which seems to be applicable and informative, regardless of the analyzer used.

A novel complete blood count-based score to screen for myelodysplastic syndrome in cytopenic patients

The diagnosis of myelodysplastic syndromes (MDS) is often challenging, time- and resource-consuming. A thorough analysis of complete blood count (CBC) parameters could, however, help to screen for MDS among other causes of cytopenia. To test this hypothesis, 109 newly-diagnosed MDS patients and 399 cytopenic patients older than 50 years with confirmed absence of MDS were enrolled in a prospective study. Multiparametric analysis highlighted three CBC parameters that were significantly different between the two cohorts: mean corpuscular volume, absolute neutrophil count and median neutrophil complexity and width of dispersion of the events measured (Ne-WX), which were used to define an MDS-CBC score. This score enables the prediction of MDS with 86% sensitivity and 88% specificity. The MDS-CBC score excluded MDS in 89% of cytopenic controls. Moreover, high score values at MDS diagnosis significantly correlated with decreased event-free (P = 0·02) and overall survival (P = 0·01). The power of this score was confirmed in an independent validation cohort (MDS n = 34, cytopenic controls n = 28). The MDS-CBC score is an easy and fast tool to exclude or suspect MDS in unselected patients with cytopenia of unknown reasons at the time of analysis, by prompting blood smear examination. It may thus improve allocation of further MDS-specific work-up in patients with cytopenia at the time of CBC assessment.

Implementation of the Ogata flow cytometric scoring system in routine diagnostics of myelodysplastic syndrome

BACKGROUND AND AIMS

Compiling evidence has emerged for the relevance of flow cytometric assessment as a valuable part of the diagnostic work-up of myelodysplastic syndrome (MDS). This study aimed at evaluating the implementation of a simple flow cytometric scoring system (FCSS), the Ogata score, in a routine diagnostic laboratory.

METHODS

A total of 35 patient samples with a clinical suspicion of MDS were retrospectively assessed using the FCSS. The accuracy of the FCSS was evaluated on the basis of the final diagnoses of the patients.

RESULTS

The final diagnoses included 17 MDS, 4 other myeloid cancers, and 14 reactive changes. Thirty-two of 35 (91%) were correctly scored by the FCSS. All 3 incorrect scores were from samples classified as "other myeloid cancers." Of the initial pathological evaluation of the bone marrows, 20% were inconclusive or incorrect. All inconclusive samples were correctly scored using the FCSS.

CONCLUSION

The FCSS evaluated here has high accuracy and low complexity. Cases with inconclusive pathological evaluation will especially potentially benefit from adding the Ogata score to the diagnostic work-up. The system will be feasible to implement in most flow cytometry laboratories without the need for supplemental antibody panels. It should be emphasized that the FCSS, in our hands, provided poor discrimination between MDS and other myeloid clonal diseases.

Dyserythropoiesis evaluated by the RED score and hepcidin:ferritin ratio predicts response to erythropoietin in lower-risk myelodysplastic syndromes

Erythropoiesis-stimulating agents are generally the first line of treatment of anemia in patients with lower-risk myelodysplastic syndrome. We prospectively investigated the predictive value of somatic mutations, and biomarkers of ineffective erythropoiesis including the flow cytometry RED score, serum growth-differentiation factor-15, and hepcidin levels. Inclusion criteria were no prior treatment with erythropoiesis-stimulating agents, low- or intermediate-1-risk myelodysplastic syndrome according to the International Prognostic Scoring System, and a hemoglobin level <10 g/dL. Patients could be red blood cell transfusion-dependent or not and were given epoetin zeta 40 000 IU/week. Serum erythropoietin level, iron parameters, hepcidin, flow cytometry Ogata and RED scores, and growth-differentiation factor-15 levels were determined at baseline, and molecular analysis by next-generation sequencing was also conducted. Erythroid response (defined according to the International Working Group 2006 criteria) was assessed at week 12. Seventy patients, with a median age of 78 years, were included in the study. There were 22 patients with refractory cytopenia with multilineage dysplasia, 19 with refractory cytopenia with unilineage dysplasia, 14 with refractory anemia with ring sideroblasts, four with refractory anemia with excess blasts-1, six with chronic myelomonocytic leukemia, two with del5q-and three with unclassifiable myelodysplastic syndrome. According to the revised International Prognostic Scoring System, 13 had very low risk, 47 had low risk, nine intermediate risk and one had high-risk disease. Twenty patients were transfusion dependent. Forty-eight percent had an erythroid response and the median duration of the response was 26 months. At baseline, non-responders had significantly higher RED scores and lower hepcidin:ferritin ratios. In multivariate analysis, only a RED score >4 (P=0.05) and a hepcidin:ferritin ratio <9 (P=0.02) were statistically significantly associated with worse erythroid response. The median response duration was shorter in patients with growth-differentiation factor-15 >2000 pg/mL and a hepcidin:ferritin ratio <9 (P=0.0008 and P=0.01, respectively). In multivariate analysis, both variables were associated with shorter response duration. Erythroid response to epoetin zeta was similar to that obtained with other erythropoiesis-stimulating agents and was correlated with higher baseline hepcidin:ferritin ratio and lower RED score. ClinicalTrials.gov registration: NCT 03598582.

[Value of multiparameter flow cytometry in the diagnosis and prognostic evaluation of childhood myelodysplastic syndrome]

OBJECTIVE

To investigate the value of multiparameter flow cytometry (MFC) and flow cytometric scoring system (FCSS) in the diagnosis and prognostic evaluation of childhood myelodysplastic syndrome (MDS).

METHODS

A retrospective analysis was performed for the clinical data of 42 children who were diagnosed with MDS. MFC was performed to investigate the phenotype and proportion of each lineage of bone marrow cells. The correlations of FCSS score with MDS type, International Prognostic Scoring System (IPSS) score, and revised IPSS (IPSS-R) score were analyzed.

RESULTS

Of all the 42 children, 20 (48%) had an increase in abnormal marrow blasts, 19 (45%) had a lymphoid/myeloid ratio of >1, 14 (33%) had abnormal cross-lineage expression of lymphoid antigens in myeloid cells, 8 (19%) had abnormal CD13/CD16 differentiation antigens, 5 (12%) had abnormal expression of CD56, 3 (7%) had reduced or increased side scatter of granulocytes, 3 (7%) had reduced expression of CD36 in nucleated red blood cells, 2 (5%) had reduced expression of CD71 in nucleated red blood cells, 1 (2%) had absent expression of CD33 in myeloid cells, 1 (2%) had reduced or absent expression of CD11b in granulocytes, and 1 (2%) had absent expression of CD56 and CD14 in monocytes. There were significant differences in the median overall survival time and event-free survival time among the low-, medium-, and high-risk FCSS groups (P<0.05). Among the low-, medium-, and high-risk FCSS groups, the low-risk FCSS group had the highest 2-year overall survival rate, while there was no significant difference between the medium- and high-risk FCSS groups (P>0.05). The three groups had a 2-year event-free survival rate of 95%, 60%, and 46% respectively (P<0.05). FCSS score was positively correlated with MDS type, IPSS score, and IPSS-R score (P<0.05).

CONCLUSIONS

MFC and FCSS help with the diagnosis and prognostic evaluation of childhood MDS.

Clinical Implication of Multi-Parameter Flow Cytometry in Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a challenging group of diseases for clinicians and researchers, as both disease course and pathobiology are highly heterogeneous. In (suspected) MDS patients, multi-parameter flow cytometry can aid in establishing diagnosis, risk stratification and choice of therapy. This review addresses the developments and future directions of multi-parameter flow cytometry scores in MDS. Additionally, we propose an integrated diagnostic algorithm for suspected MDS.

Usability of femoral head bone marrow to verify reference ranges for the assessment of myelodysplasia by flow cytometry

BACKGROUND

A flow cytometry score (FCS) based on four parameters has been proposed for analysis of myelodysplastic syndromes patients with <5% blasts. We evaluated whether bone marrow aspirate samples isolated from femoral heads could be used for verification of cutoff values of the individual parameters score (IPS), contributing to the FCS and compared the applicability of FCS parameters in two centers.

STUDY DESIGN AND METHODS

Bone marrow cells were obtained from femoral heads of patients who underwent hip replacement surgery. The score of the 4 individual parameters of the cell samples were obtained independently in two centers, using their own facilities and methods. Flow cytometry data files were subsequently exchanged and reanalyzed in the other center. The resulting four data sets were compared to assess reproducibility and outcomes in both centers.

RESULTS

Twenty-nine of 40 bone marrow samples contained sufficient cells for analysis. Proposed cutoff values for 3 of 4 individual parameters were appropriate. All 29 samples showed a positive individual parameters score (IPS:1) in 1 of the 4 obtained data sets. Most differences in IPS scores were a result of reanalyzing the data file in the other center, rather than data acquisition. FCS: ≥2 were observed in 11 samples.

CONCLUSION

Bone marrow samples from femoral heads are appropriate for verification of the proposed reference cutoff values of the individual parameters. Proposed reference cutoff values needed to be adjusted for reliable interpretation. Standardization of both data acquisition and data analysis is necessary for obtaining uniform results.

The impact of delayed sample handling and type of anticoagulant on the interpretation of dysplastic signs detected by flow cytometry

Introduction

A growing body of evidence supports the usefulness of dysplastic signs detected by flow cytometry in the diagnosis of myelodysplastic syndromes (MDS). Our aim was to assess the impact of pre-analytical variables (delayed sample handling, type of anticoagulant, and different clones of antibody) in the interpretation of flow cytometric results.

Material and methods

Bone marrow samples were labelled and analysed immediately after aspiration and on two consecutive days. The effect of anticoagulant type was evaluated in 16 bone marrow samples. Thirty-seven different immunophenotypic variables were recorded after eight-colour staining. Furthermore, 8 normal peripheral blood samples collected in K₃-EDTA and Na-heparin were examined with different clones of CD11b antibodies and four parameters were recorded with both anticoagulants on two consecutive days.

Results

Fourteen significant differences were detected in the initial immunophenotype of fresh samples collected in K₃-EDTA and Na-heparin. Regardless of the anticoagulant type, eleven parameters remained stable despite delayed sample handling. Due to delayed sample processing, more alterations were detected in the samples collected in K₃-EDTA than in the samples collected in Na-heparin. The type of CD11b clone influenced the reduction of fluorescence intensity only in samples collected in K₃-EDTA, where the alterations were contrary to the changes observed in Na-heparin.

Conclusions

Delayed sample processing causes considerable immunohenotypic alterations, which can lead to false interpretation of the results. If delayed sample evaluation is unavoidable, markers that remain more stable over time should be considered with more weight in the diagnosis of MDS.