Standardization of flow cytometry in myelodysplastic syndromes: a report from an international consortium and the European LeukemiaNet Working Group

Determinants of lenalidomide response with or without erythropoiesis-stimulating agents in myelodysplastic syndromes: the HOVON89 trial

A randomized phase-II study was performed in low/int-1 risk MDS (IPSS) to study efficacy and safety of lenalidomide without (arm A) or with (arm B) ESA/G-CSF. In arm B, patients without erythroid response (HI-E) after 4 cycles received ESA; G-CSF was added if no HI-E was obtained by cycle 9. HI-E served as primary endpoint. Flow cytometry and next-generation sequencing were performed to identify predictors of response. The final evaluation comprised 184 patients; 84% non-del(5q), 16% isolated del(5q); median follow-up: 70.7 months. In arm A and B, 39 and 41% of patients achieved HI-E; median time-to-HI-E: 3.2 months for both arms, median duration of-HI-E: 9.8 months. HI-E was significantly lower in non-del(5q) vs. del(5q): 32% vs. 80%. The same accounted for transfusion independency-at-week 24 (16% vs. 67%), but similar in both arms. Apart from presence of del(5q), high percentages of bone marrow lymphocytes and progenitor B-cells, a low number of mutations, absence of ring sideroblasts, and SF3B1 mutations predicted HI-E. In conclusion, lenalidomide induced HI-E in patients with non-del(5q) and del(5q) MDS without additional effect of ESA/G-CSF. The identified predictors of response may guide application of lenalidomide in lower-risk MDS in the era of precision medicine. (EudraCT 2008-002195-10).

Imaging Flow Cytometry: Development, Present Applications, and Future Challenges

Imaging flow cytometry (ImFC) represents a significant technological advancement in the field of cytometry, effectively merging the high-throughput capabilities of flow analysis with the detailed imaging characteristics of microscopy. In our comprehensive review, we adopt a historical perspective to chart the development of ImFC, highlighting its origins and current state of the art and forecasting potential future advancements. The genesis of ImFC stemmed from merging the hydraulic system of a flow cytometer with advanced camera technology. This synergistic coupling facilitates the morphological analysis of cell populations at a high-throughput scale, effectively evolving the landscape of cytometry. Nevertheless, ImFC's implementation has encountered hurdles, particularly in developing software capable of managing its sophisticated data acquisition and analysis needs. The scale and complexity of the data generated by ImFC necessitate the creation of novel analytical tools that can effectively manage and interpret these data, thus allowing us to unlock the full potential of ImFC. Notably, artificial intelligence (AI) algorithms have begun to be applied to ImFC, offering promise for enhancing its analytical capabilities. The adaptability and learning capacity of AI may prove to be essential in knowledge mining from the high-dimensional data produced by ImFC, potentially enabling more accurate analyses. Looking forward, we project that ImFC may become an indispensable tool, not only in research laboratories, but also in clinical settings. Given the unique combination of high-throughput cytometry and detailed imaging offered by ImFC, we foresee a critical role for this technology in the next generation of scientific research and diagnostics. As such, we encourage both current and future scientists to consider the integration of ImFC as an addition to their research toolkit and clinical diagnostic routine.

Aberrant myelomonocytic CD56 expression predicts response to cyclosporine therapy in pediatric patients with moderate aplastic anemia

Objects

This study aimed to investigate the expression patterns and clinical significance of neural cell adhesion molecule-positive (CD56+) myelomonocytes in pediatric patients with moderate aplastic anemia (mAA).

Methods

Fifty-six pediatric patients with mAA were enrolled in this study. The patients' clinical characteristics, laboratory data, and response to cyclosporine therapy were obtained. CD56 expression on bone marrow myelomonocytic cells was investigated using flow cytometry. The association between aberrant CD56 expression and cyclosporine response was evaluated by a multivariate analysis.

Results

CD56+ myelomonocytes were detected in 43% of the mAA cases. Aberrant CD56 expression was frequent on immature CD45dimCD16dim granulocytes and mature CD45brightCD14bright monocytes. Compared with patients with CD56- myelomonocytes (CD56- patients), patients with CD56+ myelomonocytes (CD56+ patients) were in moderate hematological condition and had a distinct bone marrow cellular composition profile, which included an increased proportion of myeloid cells and CD56bright natural killer cells and a reduced proportion of CD4+ T cells, CD8+ T cells, and B cells. The multivariate analysis determined that CD56+ myelomonocytes were a favorable factor for achieving response at 6 months after cyclosporine therapy. There was a trend towards a lower 3-year rate of evolution to severe aplastic anemia or relapse among the CD56+ patients (8%) than the CD56- patients (22%).

Conclusion

CD56+ patients had an increased myeloid compartment and better prognosis compared with CD56- patients. The findings demonstrated the favorable role of CD56+ myelomonocytes in aplastic anemia progression.

Measurable residual disease monitoring in patients with acute myeloid leukemia treated with lower-intensity therapy: Roadmap from an ELN-DAVID expert panel

With the availability of effective targeted agents, significant changes have occurred in the management of patients with acute myeloid leukemia (AML) over the past several years, particularly for those considered unfit for intensive chemotherapy. While testing for measurable residual disease (MRD) is now routinely performed in patients treated with intensive chemotherapy to refine prognosis and, possibly, inform treatment decision-making, its value in the context of lower-intensity regimens is unclear. As such regimens have gained in popularity and can be associated with higher response rates, the need to better define the role of MRD assessment and the appropriate time points and assays used for this purpose has increased. This report outlines a roadmap for MRD testing in patients with AML treated with lower-intensity regimens. Experts from the European LeukemiaNet (ELN)-DAVID AML MRD working group reviewed all available data to propose a framework for MRD testing in future trials and clinical practice. A Delphi poll served to optimize consensus. Establishment of uniform standards for MRD assessments in lower-intensity regimens used in treating patients with AML is clinically relevant and important for optimizing testing and, ultimately, improving treatment outcomes of these patients.

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.

Childhood Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) in children is rare, accounting for < 5% of all childhood hematologic malignancies. With the advent of next-generation sequencing, the etiology of many childhood MDS (cMDS) cases has been elucidated with the finding of predisposing germline mutations in one-quarter to one-third of cases; somatic mutations have also been identified, indicating that cMDS is different than adult MDS. Herein, cMDS classification schema, clinical presentation, laboratory values, bone marrow histology, differential diagnostic considerations, and the recent molecular findings of cMDS are described.

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.

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.

The European Guidelines on Diagnosis and Management of Neutropenia in Adults and Children: A Consensus Between the European Hematology Association and the EuNet-INNOCHRON COST Action

Neutropenia, as an isolated blood cell deficiency, is a feature of a wide spectrum of acquired or congenital, benign or premalignant disorders with a predisposition to develop myelodysplastic neoplasms/acute myeloid leukemia that may arise at any age. In recent years, advances in diagnostic methodologies, particularly in the field of genomics, have revealed novel genes and mechanisms responsible for etiology and disease evolution and opened new perspectives for tailored treatment. Despite the research and diagnostic advances in the field, real world evidence, arising from international neutropenia patient registries and scientific networks, has shown that the diagnosis and management of neutropenic patients is mostly based on the physicians' experience and local practices. Therefore, experts participating in the European Network for the Innovative Diagnosis and Treatment of Chronic Neutropenias have collaborated under the auspices of the European Hematology Association to produce recommendations for the diagnosis and management of patients across the whole spectrum of chronic neutropenias. In the present article, we describe evidence- and consensus-based guidelines for the definition and classification, diagnosis, and follow-up of patients with chronic neutropenias including special entities such as pregnancy and the neonatal period. We particularly emphasize the importance of combining the clinical findings with classical and novel laboratory testing, and advanced germline and/or somatic mutational analyses, for the characterization, risk stratification, and monitoring of the entire spectrum of neutropenia patients. We believe that the wide clinical use of these practical recommendations will be particularly beneficial for patients, families, and treating physicians.

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.

The flow cytometry myeloid progenitor count: A reproducible parameter for diagnosis and prognosis of myelodysplastic syndromes

BACKGROUND

The bone marrow blast count is central to the diagnosis and monitoring of myelodysplastic syndromes (MDS). It is an independent risk factor for worse prognosis whether based on the morphology blast count or the flow cytometry (FC) myeloid progenitor (MyP) count. It is a principal population in FC MDS analysis also because once defined; it provides significant contributions to the overall FC MDS score.

METHODS

We elected to investigate inter-analyst agreement for the most fundamental parameter of the FC MDS diagnostic score: the MyP count. A common gating strategy was agreed and used by seven cytometrists for blind analysis of 34 routine bone marrows sent for MDS work-up. Additionally, we compared the results with a computational approach.

RESULTS

Concordance was excellent: Intraclass correlation was 0.993 whether measuring %MyP of total cells or CD45+ cells, and no significant difference was observed between files from different centers or for samples with abnormal MyP phenotypes. Computational and manual results were similar. Applying the common strategy to individual laboratories' control cohorts produced similar MyP reference ranges across centers.

CONCLUSION

The FC MyP count offers a reliable diagnostic and prognostic measurement in MDS. The use of manual and computational approaches side by side may allow for optimizing both strategies. Considering its known prognostic power, the MyP count could be considered a useful and reliable addition to existing prognostic scoring systems.

Identification of a specific immunophenotype associated with a consistent pattern of genetic mutations including SRFS2 and gene expression profile in MDS

BACKGROUND

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of diseases classified by comprehensive diagnostics. Identification of homogeneous subgroups is desirable to understand differences in clinical course and to develop targeted treatment approaches. We identified a specific CD11b/CD16 expression pattern in granulocytes associated with reduced CD45 expression in myeloid progenitor cells (MPC) in MDS cases and assessed its genetic background by whole genome (WGS) and whole transcriptome sequencing (WTS).

METHODS

The cohort consisted of 32 MDS cases with the specific aberrant immunophenotype. Since all these 32 cases were found to be SRSF2 mutated additional 51 SRSF2 mutated MDS cases without this specific immunophenotype were selected as controls. For all cases WGS and WTS were performed.

RESULTS

The immunophenotype newly identified in SRSF2 mutated MDS patients is characterized (1) by a specific maturation pattern, i.e. an increase of CD11b expression without CD16 expression followed by an increase in CD16 expression without further CD11b expression and (2) by only dim CD45 expression of MPC. STAG2 mutations were exclusively found in MDS cases with the specific immunophenotype (17/32, 53% vs. 0%, p < 0.001). Hence, >50% of cases with the specific immunophenotype were characterized by co-mutations in SRSF2 and STAG2. In addition, cluster analysis revealed a specific gene expression profile of such cases.

CONCLUSION

We here for the first time describe a specific immunophenotype which defines MDS cases with SRSF2 mutations and a consistent and specific mutational and gene expression profile. This comprehensive data warrants analysis of further such cases to assess the feasibility of defining a new sub-entity of MDS.

Dysplasia and PNH-type cells in bone marrow aspirates of myelodysplastic syndromes

BACKGROUND

Flow cytometry is increasingly applied in cytopenic patients suspected for myelodysplastic syndromes (MDS). Analysis includes evaluation of antigen expression patterns in granulocytes of which, for example, partial lack of CD16 may indicate dysplasia, but presence of paroxysmal nocturnal hemoglobinuria (PNH)-type cells should be considered. However, diagnostic bone marrow (BM) samples hamper PNH analysis because immature stages in the granulo-/monocytic compartment lack expression of certain glycophosphatidyl-inositol-anchored proteins. In this prospective study, we evaluated the presence of PNH-type cells in BM next to aberrancies from routine MDS immunophenotyping.

METHODS

We combined antibodies defining maturation trajectories with FLAER. Validation of the designed method against routine PNH analysis and parallel analysis of BM and blood samples revealed similar results (granulocytes: Wilcoxon p = 0.25 and p = 0.82, respectively). We analyzed BM samples from 134 MDS, 17 chronic myelomonocytic leukemia, 15 aplastic anemia (AA), 1 PNH, 51 non-clonal cytopenic controls, and 12 normal controls.

RESULTS

Most AA/PNH-BM samples showed clear PNH clones: median 1.1% (0%-35%); CD16 loss on mature neutrophils paralleled PNH-clone sizes. In MDS-BM, only 3.7% of cases showed ≥0.1% PNH-type cells, whereas partial CD16 loss was more frequent and abundant.

CONCLUSIONS

Our findings confirm that dysplastic features in MDS-BM may point to presence of PNH-type cells, though only few cases displayed FLAER-negative cells. We showed that identification of these cells in the granulocyte compartment of BM specimen is feasible, but-according to international guidelines-results need to be confirmed in peripheral blood.

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.

Multicenter prospective evaluation of diagnostic potential of flow cytometric aberrancies in myelodysplastic syndromes by the ELN iMDS flow working group

BACKGROUND

Myelodysplastic syndromes (MDS) represent a diagnostic challenge. This prospective multicenter study was conducted to evaluate pre-defined flow cytometric markers in the diagnostic work-up of MDS and chronic myelomonocytic leukemia (CMML).

METHODS

Thousand six hundred and eighty-two patients with suspected MDS/CMML were analyzed by both cytomorphology according to WHO 2016 criteria and flow cytometry according to ELN recommendations. Flow cytometric readout was categorized 'non-MDS' (i.e. no signs of MDS/CMML and limited signs of MDS/CMML) and 'in agreement with MDS' (i.e., in agreement with MDS/CMML).

RESULTS

Flow cytometric readout categorized 60% of patients in agreement with MDS, 28% showed limited signs of MDS and 12% had no signs of MDS. In 81% of cases flow cytometric readouts and cytomorphologic diagnosis correlated. For high-risk MDS, the level of concordance was 92%. A total of 17 immunophenotypic aberrancies were found independently related to MDS/CMML in ≥1 of the subgroups of low-risk MDS, high-risk MDS, CMML. A cut-off of ≥3 of these aberrancies resulted in 80% agreement with cytomorphology (20% cases concordantly negative, 60% positive). Moreover, >3% myeloid progenitor cells were significantly associated with MDS (286/293 such cases, 98%).

CONCLUSION

Data from this prospective multicenter study led to recognition of 17 immunophenotypic markers allowing to identify cases 'in agreement with MDS'. Moreover, data emphasizes the clinical utility of immunophenotyping in MDS diagnostics, given the high concordance between cytomorphology and the flow cytometric readout. Results from the current study challenge the application of the cytomorphologically defined cut-off of 5% blasts for flow cytometry and rather suggest a 3% cut-off for the latter.

Clinical, immunophenotypic, and cytogenetic characteristics of high-grade myelodysplastic syndromes with CD41-positive progenitor cells

BACKGROUND

Patients with myelodysplastic syndromes (MDS) with progenitors expressing CD41 (CD41+ MDS) showed a poor prognosis in a previous study but their detailed characteristics remain unclear.

METHODS

One hundred thirty-seven subjects at our institution were diagnosed with excess blasts (EB)-1, EB-2, and acute myeloid leukemia with a low blast count (20%-30%). The immunophenotypes of progenitor cells in their bone marrow (BM) were determined by CD45-gating flow cytometry. A false-positive reaction to CD41 was eliminated by examining the flow cytometry data of lymphocytes and monocytes in addition to progenitors and by examining CD42b in histological sections. The characteristics were compared between CD41+ and CD41- MDS patients.

RESULTS

Forty-three patients (31%) were CD41+. Additionally, 91% of the CD41+ MDS patients were very high-risk defined by the Revised International Prognostic Score System, which was higher than in patients with CD41- MDS (p = 0.015). Approximately 60% of the CD41+ MDS patients had a monosomal karyotype and very poor cytogenetics, which was higher than in CD41- MDS patients (p < 0.001). Normal cytogenetics was less common in CD41+ patients (p = 0.0016). Blasts with bleb formation were more abundant in CD41+ MDS patients (p = 0.026). All CD41+ MDS patients were positive for CD13 and were mostly positive for CD33. The frequency of aberrant expression of other antigens on progenitors was similar between CD41+ and CD41- MDS patients.

CONCLUSIONS

We determined clinical, immunophenotypic, and cytogenetic characteristics of CD41+ MDS patients. Further studies are needed to improve the survival of these patients.

Management of patients with lower-risk myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of hematopoietic stem cell disorders characterized by ineffective hematopoiesis with abnormal blood cell development (dysplasia) leading to cytopenias and an increased risk for progression to acute myeloid leukemia (AML). Patients with MDS can generally be classified as lower- (LR-MDS) or higher-risk (HR-MDS). As treatment goals for patients with LR-MDS and those with HR-MDS differ significantly, appropriate diagnosis, classification, and follow-up are critical for correct disease management. In this review, we focus on the diagnosis, prognosis, and treatment options, as well as the prediction of the disease course and monitoring of treatment response in patients with LR-MDS. We discuss how next-generation sequencing, increasing knowledge on mechanisms of MDS pathogenesis, and novel therapies may change the current treatment landscape in LR-MDS and why structured assessments of responses, toxicities, and patient-reported outcomes should be incorporated into routine clinical practice.

Comparison of the revised 4th (2016) and 5th (2022) editions of the World Health Organization classification of myelodysplastic neoplasms

We used data from 852 consecutive subjects with myelodysplastic neoplasms (MDS) diagnosed according to the 2016 (revised 4th) World Health Organization (WHO) criteria to evaluate the 2022 (5th) edition WHO classification of MDS. 30 subjects previously classified as MDS with an NPM1 mutation were re-classified as acute myeloid leukaemia (AML). 9 subjects previously classified as MDS-U were re-classified to clonal cytopenia of undetermined significance (CCUS). The remaining 813 subjects were diagnosed as: MDS-5q (N = 11 [1%]), MDS-SF3B1 (N = 70 [9%]), MDS-biTP53 (N = 53 [7%]), MDS-LB (N = 293 [36%]), MDS-h (N = 80 [10%]), MDS-IB1 (N = 161 [20%]), MDS-IB2 (N = 103 [13%]) and MDS-f (N = 42 [5%]) and MDS-biTP53 (N = 53 [7%]). 34 of these subjects came from the 53 (64%) MDS-biTP53 previously diagnosed as MDS-EB. Median survival of subjects classified as MDS using the WHO 2022 criteria was 45 months (95% Confidence Interval [CI], 34, 56 months). Subjects re-classified as MDS-biTP53 and MDS-f had significantly briefer median survivals compared with other MDS sub-types (10 months, [8, 12 months] and 15 months [8, 23 months]). In conclusion, our analyses support the refinements made in the WHO 2022 proposal.

Inter-intra instrument comparison and standardization of a 10-color immunophenotyping for B and T cell non-Hodgkin lymphoma diagnosis and monitoring

Harmonization of flow cytometry protocols from instrument settings to antibody panel and reagents is highly encouraged for inter-laboratory data comparison in both research and clinical settings, especially for minimal residual disease monitoring evaluation in hematological diseases across centers. Here, we described inter-intra instrument comparison of two standardized 10-color staining dried tubes for B- and T-cell lymphoproliferative disorder diagnosis and monitoring on two different flow cytometers, a Beckman Coulter NaviosEx and a Beckman Coulter DxFlex. A total of 47 consecutive patients were enrolled, and 39 of them were evaluable for further studies. We show highly comparable results between the two cytometers for cell frequency and fluorescence intensity signals for both standardized 10-color staining dried tubes. For this latter, fluorescence of each antibody and subject was normalized on the mean value obtained from the entire study cohort thus reducing the effects of biological variability and allowing comparison between instruments with different detector sensitivity. In summary, dried tubes were confirmed as an optimal standardized diagnostic tool, especially when associated with EuroFlow standardized procedures by minimizing technical and biological variability. However, data analysis is still operator-dependent, and more efforts are needed to develop automated or semi-automated software for flow cytometry data analysis for diagnostic purposes.

The Impact of Clonal Hierarchy and Heterogeneity on Phenotypic Manifestations of Myelodysplastic Neoplasms

Until recently, conventional prognostication of myelodysplastic neoplasms (MDS) was performed using the revised International Prognostic Scoring System (IPSS-R), with additional adverse prognoses conferred by select mutations. Nonetheless, the clonal diversity and dynamics of coexisting mutations have been shown to alter the prognosis and treatment response in patients with MDS. Often in the process of clonal evolution, various initial hits are preferentially followed by a specific spectrum of secondary alterations, shaping the phenotypic and biologic features of MDS. Our ability to recapitulate the clonal ontology of MDS is a necessary step toward personalized therapy and the conceptualization of a better classification system, which ideally would take into consideration all genomic aberrations and their inferred clonal architecture in individual cases. In this review, we summarize our current understanding of the molecular landscape of MDS and the role of mutational combinations, clonal burden, and clonal hierarchy in defining the clinical fate of the disease.

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.

Myelodysplastic Syndrome: Diagnosis and Screening

Myelodysplastic syndromes (MDS) are heterogeneous groups of clonal myeloid disorders characterized by unexplained persistent peripheral blood (PB) cytopenia(s) of one or more of the hematopoietic lineages, or bone marrow (BM) morphologic dysplasia in hematopoietic cells, recurrent genetic abnormalities, and an increased risk of progression to acute myeloid leukemia (AML). In the past several years, diagnostic, prognostic, and therapeutic approaches have substantially improved with the development of Next Generation Sequencing (NGS) diagnostic testing and new medications. However, there is no single diagnostic parameter specific for MDS, and correlations with clinical information, and laboratory test findings are needed to reach the diagnosis.

Novel Translational Read-through-Inducing Drugs as a Therapeutic Option for Shwachman-Diamond Syndrome

Shwachman-Diamond syndrome (SDS) is one of the most commonly inherited bone marrow failure syndromes (IBMFS). In SDS, bone marrow is hypocellular, with marked neutropenia. Moreover, SDS patients have a high risk of developing myelodysplastic syndrome (MDS), which in turn increases the risk of acute myeloid leukemia (AML) from an early age. Most SDS patients are heterozygous for the c.183-184TA>CT (K62X) SBDS nonsense mutation. Fortunately, a plethora of translational read-through inducing drugs (TRIDs) have been developed and tested for several rare inherited diseases due to nonsense mutations so far. The authors previously demonstrated that ataluren (PTC124) can restore full-length SBDS protein expression in bone marrow stem cells isolated from SDS patients carrying the nonsense mutation K62X. In this study, the authors evaluated the effect of a panel of ataluren analogues in restoring SBDS protein resynthesis and function both in hematological and non-hematological SDS cells. Besides confirming that ataluren can efficiently induce SBDS protein re-expression in SDS cells, the authors found that another analogue, namely NV848, can restore full-length SBDS protein synthesis as well, showing very low toxicity in zebrafish. Furthermore, NV848 can improve myeloid differentiation in bone marrow hematopoietic progenitors, enhancing neutrophil maturation and reducing the number of dysplastic granulocytes in vitro. Therefore, these findings broaden the possibilities of developing novel therapeutic options in terms of nonsense mutation suppression for SDS. Eventually, this study may act as a proof of concept for the development of similar approaches for other IBMFS caused by nonsense mutations.

Flow Cytometric Findings in Clonal Cytopenia of Undetermined Significance

OBJECTIVES

To examine flow cytometric (FCM) findings in clonal cytopenia of undetermined significance (CCUS) in relation to variant allele fraction (VAF) and mutation risk.

METHODS

Nine FCM parameters, including 5 FCM metrics (Meyerson-Alayed scoring scheme [MASS] parameters) we previously used to identify myelodysplastic syndromes (MDS), were compared among 96 CCUS samples, 100 low-grade MDS samples and 100 samples from patients without somatic alterations (controls).

RESULTS

FCM findings did not differ between CCUS samples with less than 20% VAF and controls. CCUS samples with more than 20% VAF (CCUS >20% VAF) demonstrated more than 1 abnormal FCM parameter at a frequency between MDS and controls. Abnormalities in CCUS with high-risk alterations (CCUS(hi)) were similar to MDS, with no statistical difference in the percentage of cases with more than 1 FCM abnormality or a positive MASS score. The positive predictive value (PPV) for clinically significant myeloid processes; MDS, CCUS(hi), and CCUS >20% VAF compared with other CCUS samples and controls was 94.8%, with 96.5% specificity and 61% sensitivity using a modified MASS score. A subset of MDS (43%) was distinguished from CCUS(hi) and CCUS >20% VAF using 3 parameters, with a 93.5% PPV and 83.3% specificity.

CONCLUSIONS

FCM abnormalities can distinguish high-risk CCUS based on VAF or alteration type from low-risk CCUS and MDS in many cases. The findings are of potential utility in the evaluation of patients with cytopenias.

Technical Aspects of Flow Cytometry-based Measurable Residual Disease Quantification in Acute Myeloid Leukemia: Experience of the European LeukemiaNet MRD Working Party

Measurable residual disease (MRD) quantified by multiparameter flow cytometry (MFC) is a strong and independent prognostic factor in acute myeloid leukemia (AML). However, several technical factors may affect the final read-out of the assay. Experts from the MRD Working Party of the European LeukemiaNet evaluated which aspects are crucial for accurate MFC-MRD measurement. Here, we report on the agreement, obtained via a combination of a cross-sectional questionnaire, live discussions, and a Delphi poll. The recommendations consist of several key issues from bone marrow sampling to final laboratory reporting to ensure quality and reproducibility of results. Furthermore, the experiences were tested by comparing two 8-color MRD panels in multiple laboratories. The results presented here underscore the feasibility and the utility of a harmonized theoretical and practical MFC-MRD assessment and are a next step toward further harmonization.

Complete blood count and cell population data parameters from the Abbott Alinity hq analyzer are useful in differentiating myelodysplastic syndromes from other forms of cytopenia

INTRODUCTION

Myelodysplastic syndromes (MDS) are characterized by morphologic dysplasia and cytopenia and have a propensity for acute leukemic transformation. However, dysplasia is diagnosed by morphology, thus having cell population data (CPD) that can differentiate cytopenic patients with MDS from other conditions may facilitate accurate diagnosis. We assessed the utility of complete blood count (CBC) parameters and CPD derived from an Abbott Alinity hq analyzer to discriminate MDS-related cytopenia.

METHODS

The patient cohort (n = 345) included 64 samples from patients with MDS, 162 from patients with other cytopenia, and 119 from healthy controls. The hematological parameters and research use-only parameters of the Abbott Alinity hq analyzer were compared between the cytopenic groups. The effectiveness of the individual standard and research CBC parameters to differentiate MDS from other forms of cytopenia was assessed through a receiver operating characteristics (ROC) analysis.

RESULTS

The percentage of MAC (Macrocytic RBCs) and hemoglobin distribution width (HDW) were higher in the MDS group than in the other cytopenia group and showed the greatest difference between both groups, with an area under the curve (AUC) of 0.766 (0.678-0.855) and 0.786 (0.702-0.870), respectively. The platelet distribution width was higher in the MDS group than in the other cytopenia group, with an AUC of 0.697 (0.623-0.770). WBC CPD extracted from histograms, especially Atyp-PMN-loc and Neu-ALL-M, showed high AUCs of 0.815 (0.750-0.879) and 0.778 (0.711-0.845), respectively.

CONCLUSION

Our findings demonstrate the clinical utility of CPD and hematology parameters of the Abbott Alinity hq analyzer in the differential diagnosis of MDS.

Biology and clinical management of hypoplastic MDS: MDS as a bone marrow failure syndrome

Hypoplastic MDS is a subset of MDS characterized by marrow hypocellularity diagnosed in 10-15% of MDS patients. The pathogenesis of this disease shares features of aplastic anemia with activation of the effector T cells against hematopoietic stem and progenitor cells and high-risk MDS with acquisition of somatic mutations that provide survival and growth advantage of these cells in the inflammatory bone marrow microenvironment. Clonal evolution in hypoplastic MDS may be associated with accumulation of DNA damage and progression to AML while clonal hematopoiesis in aplastic anemia is strongly related to immune escape of the hematopoietic cells. Distinction of hypoplastic MDS from other acquired and inherited bone marrow failure syndromes is frequently challenging but it is critical for the appropriate clinical management of the patients. Treatment with immunosuppression is an important component of the clinical approach to patients with hypoplastic MDS while hypomethylating agents and early allogeneic bone marrow transplantation are also considerations in some patients. In this review, we summarize the current literature on the biology of hypoplastic MDS, the differences between this disease and other bone marrow failure syndromes, and the treatment algorithm for patients with this subtype of MDS.

miR-378-3p Knockdown Recapitulates Many of the Features of Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are clonal neoplasms of the hematopoietic stem cell that result in aberrant differentiation of hematopoietic lineages due to a wide range of underlying genetic, epigenetic, and other causes. Despite the myriad etiologies, there is a recognizable MDS phenotype that has been associated with microRNA (miRNA) aberrant expression. A model of aberrant myeloid maturation mimicking MDS that is seen in MDS has been created using a stable knockdown of miR-378-3p. This model exhibited a transcriptional profile that indicates aberrant maturation and function, showed immunophenotypic and morphologic dysplasia, and displays the aberrant growth and function that characterizes MDS. Moreover, aberrant signal transduction in response to stimulation was demonstrated that is specific to the stage of myeloid maturation and mimics that seen in MDS patient samples using mass cytometry (CyTOF). The aberrant signaling, immunophenotypic changes, cellular growth, and colony formation ability seen in this myeloid model could be reversed with azacytidine (AZA) albeit without significant improvement of neutrophil function.

The utility of a single tube 10-color flow cytometry for quantitative and qualitative analysis in myelodysplastic syndrome- a pilot study

INTRODUCTION

Assessment of myelodysplasia (MDS) by flow cytometry (FCM) includes elaborate panels, and interpretation is observer-dependent. This study evaluates single tube 10-color FCM in a test cohort of clinically suspected MDS patients.

METHODS

We analyzed fifty-six bone marrow (BM) samples from clinically suspected MDS patients in a morphology-blinded manner along with controls using a 10-color single tube flow cytometry. We analyzed the reproducibility of Ogata score and modified FCM scores, additionally incorporating the proportion of CD15, CD11b, CD56, and CD38MFI on CD34+CD19-cluster for each patient. Patients were grouped as proven-MDS, suspected-MDS, and non-MDS groups based on morphology and cytogenetics. Optimized multi-axial radar-plots were also used to analyze maturation patterns in the granulocytic, monocytic, and blast progenitor compartments of proven-MDS cases and controls.

RESULTS

Flow cytometric abnormalities ≥3 were present in proven-MDS (n = 23) with a sensitivity and specificity of 78 % and 94 %, respectively, as per Ogata score. The addition of CD38 MFI to the score yielded sensitivity and specificity of 82 % and 88 %, respectively. Additional analysis of aberrant expression of CD15, CD11b, and CD56 increased the diagnostic power of the FCM score. A qualitative analysis of data also showed differences in maturation patterns in proven-MDS compared to the control group.

CONCLUSION

Single tube 10-color FCM scoring, including Ogata score, modified-FCM scores, and radar plots pattern analysis, showed significant abnormalities in proven-MDS cases in this pilot study. Large databases, including FCM-scoring and pattern-based analysis for normal BM maturation, could be further validated and standardized for screening MDS.

How I investigate dysgranulopoiesis

Dysgranulopoiesis is a condition in which granulocytic production is defective and is most often described in neoplastic conditions. However, it can also be frequently seen in non-neoplastic conditions. Early suspicion and detection of these non-neoplastic causes may prevent further invasive and expensive interventions. In this review, we take a look at the various causes of dysgranulopoiesis with an emphasis on non-neoplastic etiologies, followed by a detailed outline of the laboratory approach for determining its many causes.

Aberrant myelomonocytic CD56 expression in Down syndrome is frequent and not associated with leukemogenesis

Children with Down syndrome (DS) are at an increased risk of developing transient abnormal myelopoiesis (TAM) and acute leukemia. Aberrant expression of CD56 has been observed on myeloid leukemic blasts in DS patients. In general, CD56 expression in acute myeloid leukemia (AML) is considered a promoter of leukemogenesis. We did a retrospective flow cytometric study to investigate mature myelomonocytic cell CD56 expression patterns in TAM, non-TAM, and leukemia cases with DS. Flow cytometric analysis showed that granulocyte and monocyte aberrant/dysplastic CD56 expression is an inherent characteristic of most DS patients irrespective of the presence of TAM or leukemia. Increased CD56 expression in monocyte and granulocyte populations in DS could be multifactorial; greater expression of RUNX1 secondary to the gene dose effect of trisomy 21 along with the maturational state of the cells are the potential contributors. Unlike AML seen in non-DS patients, CD56 overexpression in DS AML cases does not appear to play a role in leukemogenesis.

When Should We Think of Myelodysplasia or Bone Marrow Failure in a Thrombocytopenic Patient? A Practical Approach to Diagnosis

Thrombocytopenia can arise from various conditions, including myelodysplastic syndromes (MDS) and bone marrow failure (BMF) syndromes. Meticulous assessment of the peripheral blood smear, identification of accompanying clinical conditions, and characterization of the clinical course are important for initial assessment of unexplained thrombocytopenia. Increased awareness is required to identify patients with suspected MDS or BMF, who are in need of further investigations by a step-wise approach. Bone marrow cytomorphology, histopathology, and cytogenetics are complemented by myeloid next-generation sequencing (NGS) panels. Such panels are helpful to distinguish reactive cytopenia from clonal conditions. MDS are caused by mutations in the hematopoietic stem/progenitor cells, characterized by cytopenia and dysplasia, and an inherent risk of leukemic progression. Aplastic anemia (AA), the most frequent acquired BMF, is immunologically driven and characterized by an empty bone marrow. Diagnosis remains challenging due to overlaps with other hematological disorders. Congenital BMF, certainly rare in adulthood, can present atypically with thrombocytopenia and can be misdiagnosed. Analyses for chromosome fragility, telomere length, and germline gene sequencing are needed. Interdisciplinary expert teams contribute to diagnosis, prognostication, and choice of therapy for patients with suspected MDS and BMF. With this review we aim to increase the awareness and provide practical approaches for diagnosis of these conditions in suspicious cases presenting with thrombocytopenia.

Flow cytometric immunophenotypic alterations of persistent clonal haematopoiesis in remission bone marrows of patients with NPM1-mutated acute myeloid leukaemia

Clonal haematopoiesis (CH) in patients with acute myeloid leukaemia (AML) may persist beyond attaining complete remission. From a consecutive cohort of 67 patients with nucleophosmin 1-mutated (NPM1^mut ) AML, we identified 50 who achieved NPM1^mut clearance and had parallel multicolour flow cytometry (MFC) and next generation sequencing (NGS). In total, 13 (26%) cleared all mutations, 37 (74%) had persistent CH frequently involving DNA methyltransferase 3α (DNMT3A,70%), tet methylcytosine dioxygenase 2 (TET2, 27%), isocitrate dehydrogenase 2 (IDH2, 19%) and IDH1 (11%). A small number (<1%) of aberrant CD34⁺ myeloblasts, but immunophenotypically different from original AML blasts [herein referred to as a pre-leukaemic (PL) phenotype], was detected in 17 (49%) patients with CH, but not in any patients with complete clearance of all mutations (P = 0·0037). A PL phenotype was associated with higher mutation burden (P = 0·005). Persistent IDH2 and serine and arginine-rich splicing factor 2 (SRSF2) mutations were exclusively observed in PL⁺ CH⁺ cases (P = 0·016). Persistent dysplasia was seen exclusively in cases with a PL⁺ phenotype (29% vs. none; P = 0·04). The PL⁺ phenotype did not correlate with age, intensity of induction therapy or relapse-free survival. Post-remission CH in the setting of NPM1^mut clearance is common and may result in immunophenotypic changes in myeloid progenitors. It is important to not misinterpret these cells as AML measurable residual disease (MRD).

The diagnostic and prognostic significance of flow cytometric bone marrow assessment in myelodysplastic syndromes according to the European LeukemiaNet recommendations in single-centre real-life experience

INTRODUCTION

This analysis attempts to determine the diagnostic and prognostic value of bone marrow (BM) evaluation by multiparameter flow cytometry in patients with myelodysplastic syndrome (MDS).

MATERIALS AND METHODS

The study group consisted of patients who underwent diagnostic process in the years 2008-2017 due to cytopenia and finally were diagnosed with MDS (n = 71). The comparative group included patients with cytopenia diagnosed in the same period, whose definitive diagnosis was other than MDS (n = 39). Flow cytometric evaluation of BM was performed following the recommendations of the European LeukemiaNet (ELN) in all patients.

RESULTS

The median number of immunophenotypic abnormalities found on granulocytes in the MDS group was significantly higher compared to the comparative group [2 (range 0-5) vs 0 (range 0-2); P < .0001]. Similarly, the median Ogata score was significantly higher in the MDS group [2 (range 0-4) vs 1 (range 0-3); P < .0001]. Since the disturbances of the CD11b/HLA-DR and CD11b/CD13 on granulocytes were significantly more common in MDS patients, the Ogata score was extended by these abnormalities, what resulted in its higher diagnostic sensitivity (82%) while preserving high specificity (87%). The positive correlation was found between risk score determined by the Revised International Prognostic Scoring System and the number of the BM immunophenotypic abnormalities (P = .017).

CONCLUSIONS

Our results indicate that the diagnostic usefulness of the Ogata score may be increased by including the abnormal expression of CD11b/HLA-DR and CD11b/CD13 on granulocytes. Moreover, our findings suggest the prognostic significance of the number of BM cytometric abnormalities in MDS.

The influence of fixation of biological samples on cell count and marker expression stability in flow cytometric analyses

The most common applications of flow cytometry (FC) include diagnostics of haemato-oncological disorders, based on analysis of bone marrow, peripheral blood (PB), or cerebrospinal fluid (CSF) samples. A proper diagnostic process requires standardisation in setting the optimal time frame between material collection and the assay. Unfortunately, this might be difficult to achieve in daily practice due to unintended shipment delays, which might compromise large-scale multicentre studies. Thus, material fixation should be considered as a solution. The most widely used fixative agents are: paraformaldehyde, TransFix^®, Cyto-Chex^®, and serum-containing media. In this review, we attempted to summarise the literature data on the influence of sample storage under different temperatures and times combined with different fixation conditions on the cell count and marker expression levels. Based on the findings of several extensive studies employing fixed PB samples, it can be concluded that the performance of particular fixative greatly depends on the analysed marker and specific PB cell population expressing a given antigen. Preservation of absolute cell count was usually better in Cyto-Chex^®-fixed PB samples, whereas TransFix^® tended to better stabilise marker expression levels. CSF-based studies reveal that both serum-containing media and TransFix^® can prevent cellular loss and enhance FC-based detection of leptomeningeal localisations of haematological malignancies, the latter being more available and having longer shelf-life. As both cell count and marker expression level are the main determinants of quality of biological samples dedicated to FC analyses, it remains to be addressed by the investigators which is the fixative of choice for their specific research aims.

Monitoring treatment with 5-Azacitidine by flow cytometry predicts duration of hematological response in patients with myelodysplastic syndrome

5-Azacitidine (AZA) therapy is used in high-risk myelodysplastic syndrome (MDS) patients who often show abnormalities in their immunophenotype. We explored the potential impact of AZA on these immunophenotypic abnormalities in serial bone marrow studies performed in 81 patients from five centers. We compared the immunophenotypic features before and after therapy with AZA, established definitions consistent with flow cytometry immunophenotyping (FCI) improvement, and explored its clinical significance. After a median of 6 cycles of AZA, 41% of patients showed a FCI improvement and this finding associated with best possible clinical response (P < 0.001). FCI improvement also correlated with hematological improvement (HI) (53/78 patients; 68%), independently of their eligibility for stem cell transplantation. Among patients who achieved a HI after 6 cycles of AZA, the probability of maintaining this response at 12 cycles of AZA was twice as large (67%) for those patients who also achieved a FCI improvement after 6 cycles of AZA as compared to patients who did not (33%, P < 0.01). These findings support that monitoring of the immunophenotypic abnormalities during therapy with AZA may assist in redefining the quality of response in patients with MDS.

Evaluation of multiparametric flow cytometry in diagnosis & prognosis of myelodysplastic syndrome in India

Background & objectives:

Diagnosis of myelodysplastic syndromes (MDS) is subjective in low-grade cases with <5 per cent blasts or <15 per cent ring sideroblasts. Flow cytometry (FCM) has been used to diagnose MDS; but, it still has only an adjunctive role. This study was conducted to evaluate the role of FCM to diagnose MDS and correlate the number of aberrancies with revised international prognostic scoring system (R-IPSS).

Methods:

This study included 44 consecutive clinically suspected cases of MDS with refractory cytopenia(s) and 10 controls. Patients were divided into two groups: (i) proven MDS cases (n=26), and (ii) suspected MDS (n=18). Ogata quantitative approach, pattern analysis and aberrant antigen expression were studied.

Results:

Ogata score ≥2 correctly diagnosed 80.7 per cent (21/26) while aberrant antigen and pattern analysis with flow score of ≥3 could diagnose 92.3 per cent (24/26) patients with proven MDS. Combination of both with flow score ≥3 could diagnose 100 per cent patients. Eight patients in suspected MDS group with persistent cytopenia on follow up were labelled as probable MDS. Ogata score ≥2 was present in 5 of 8 and pattern analysis score ≥3 was present in six probable MDS patients. Combination of both with flow score ≥3 was present in seven of eight patients. Spearman's correlation between Ogata score and R-IPSS, pattern analysis and R-IPSS and combination of both scores and R-IPSS showed significant positive correlation in proven MDS as well as when proven and probable MDS patients were combined.

Interpretation & conclusions:

Our results showed that combined Ogata approach and pattern analysis, demonstration of ≥3 aberrancies in >1 cell compartment could diagnose most MDS patients. Patients with high flow scores had high R-IPSS scores. Patient with flow score ≥3 and borderline cytomorphology should be observed closely for the development of MDS.

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.

Immunophenotypic characteristics of juvenile myelomonocytic leukaemia and their relation with the molecular subgroups of the disease

The diagnosis of juvenile myelomonocytic leukaemia (JMML) is based on clinical, laboratory and molecular features but immunophenotyping [multiparametric flow cytometry (MFC)] has not been used routinely. In the present study, we describe the flow cytometric features at diagnosis with special attention to the distribution of monocytic subsets and the relation between MFC and molecular subgroups. MFC was performed with an eight-colour platform based on Euroflow. We studied 33 JMML cases. CD34⁺ /CD117⁺ /CD13⁺ cells >2% was found in 25 cases, and 51·5% presented an aberrant expression of CD7. A decrease of CD34⁺ /CD19⁺ /CD10⁺ cells was seen in eight cases and in four they were absent. The granulocytic population had a decreased side scatter in 29 cases. Bone marrow monocytic precursors were increased in 28 patients, with a decrease in classical monocytes (median 80·7%) and increase in CD16⁺ (intermediate and non-classical). A more pronounced increase in myeloid CD34⁺ cells was seen in patients with Neurofibromatosis type 1 (NF1) and tyrosine-protein phosphatase non-receptor type 11 (PTPN11), with aberrant CD7 expression in four of six and 10/12 patients respectively. Thus, JMML shows an immunophenotypic profile similar to myelodysplastic syndromes, and a different monocyte subset distribution when compared with chronic MML. MFC proved to be an important diagnostic tool that can help in differential diagnosis with other clonal diseases with monocytosis.

How I Diagnose Low-Grade Myelodysplastic Syndromes

OBJECTIVES

Myelodysplastic syndromes (MDS) are a group of myeloid neoplasms that are often difficult to diagnose due to their pathologic and clinical heterogeneity. The key features of MDS are peripheral blood cytopenias, ineffective hematopoiesis manifesting as morphologic dysplasia, and clonal genetic abnormalities. The most difficult diagnostic dilemmas often arise in low-grade MDS cases (lacking excess blasts), which can be difficult to distinguish from other causes of cytopenia. This distinction requires the integration of information from the peripheral blood (both CBC parameters and morphology), bone marrow morphology, genetic studies, and interrogation of the clinical record to exclude secondary causes.

METHODS

We discuss the approach to the diagnosis of low-grade MDS (cases lacking increased blasts), including a diagnostic algorithm and two illustrative cases.

RESULTS

The appropriate use of ancillary studies is important to support or dispute the likelihood of low-grade MDS in conjunction with the findings of morphologic dysplasia. Interpreting the results of cytogenetics and next-generation sequencing can be challenging and must incorporate the emerging knowledge of clonal hematopoiesis of indeterminate potential.

CONCLUSIONS

The role of pathologists in integrating data from multiple sources in the diagnosis of low-grade MDS is evolving and becoming increasingly complex; in this challenging diagnostic setting, it is important to feel comfortable with uncertainty and maintain a conservative approach.