The utility of flow cytometric immunophenotyping in cytopenic patients with a non-diagnostic bone marrow: a prospective study

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.

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.

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.

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.

"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.

Combined Pathology-Driven Algorithmic Testing and Integrated Reporting for Bone Marrow Examination

CONTEXT.—

The College of American Pathologists published guideline recommending bone marrow synoptic reporting for hematologic neoplasms.

OBJECTIVE.—

To evaluate the impact of pathology-driven algorithmic testing (PDAT) with integrated reporting for bone marrow examination on test utilization, ability to render a specific World Health Organization diagnosis, and clinician satisfaction 1 year after implementation.

DESIGN.—

We reviewed the hematopathology reports, integrated synoptic reports, and ancillary test results generated during a 12-month period. The initial diagnosis from the hematopathology report was compared with the final diagnosis on the integrated synoptic reports. Test utilization data were compared with a previous year in which ancillary testing was ordered at clinician discretion. Clinicians were anonymously surveyed to assess their satisfaction with PDAT and integrated reporting.

RESULTS.—

Integrated reporting resulted in a World Health Organization diagnosis for 80 of 85 cases (94%) compared with 54 (64%) for the hematopathology report alone. Unnecessary testing decreased from 45% pre-PDAT (124 of 274 cases) to 0.7% PDAT (2 of 268 cases), and PDAT resulted in fewer omissions of necessary tests. Clinicians preferred PDAT and valued integrated reporting for a variety of reasons, including the ease of finding relevant prognostic information.

CONCLUSIONS.—

Pathology-driven algorithmic testing with integrated reporting improves the pathologist's ability to render a specific World Health Organization diagnosis and improves test utilization. Clinicians prefer PDAT to clinician-ordered testing. This is the first study to examine how synoptic reporting can modify hematologic diagnoses.

Diagnostic utility of the lymphoid screening tube supplemented with CD34 for Ogata score calculation in patients with peripheral cytopenia

OBJECTIVES

The diagnosis of myelodysplastic syndrome (MDS) is not always straightforward in the absence of objective markers such as ringed sideroblasts, an excess of blasts or clonal cytogenetic abnormalities. Moreover, the lack of specificity of morphological dysplasia makes the differentiation between MDS and other causes of peripheral cytopenia difficult. The WHO 2016 classification of MDS recognizes multiparameter flow cytometry (MFC) as an adjuvant tool for MDS diagnosis. An easily applicable MFC protocol based on CD34 and CD45 is proposed by Ogata et al. Furthermore, in the diagnostic workup of patients with peripheral cytopenia, the integration of MFC by means of a Lymphoid Screening Tube (LST) is recommended by the EuroFlow™ consortium. The aim of this study was to investigate whether the LST, supplemented with CD34, can be used to calculate the Ogata score, thereby obviating the need to run different flow cytometric tubes.

METHODS

Bone marrow samples from 108 patients with peripheral cytopenia were analyzed (MDS n = 32; non-MDS n = 76). The LST used in the present study was based on the tube designed by the EuroFlow™ consortium, but with addition of CD34 and without TCRγδ.

RESULTS

Rather low sensitivities of 55% in low-grade MDS patients and 80% in high-grade MDS patients were observed. However, a high specificity of 92% was found in the non-MDS group.

CONCLUSION

Besides screening for clonal lymphocytes, plasma cells and blasts, an LST supplemented with CD34 allows the calculation of the Ogata score as an adjuvant tool in the diagnostic workup of cytopenic patients suspected of MDS.

Immunophenotypes of Chronic Myelomonocytic Leukemia (CMML) Subtypes by Flow Cytometry: A Comparison of CMML-1 vs CMML-2, Myeloproliferative vs Dysplastic, De Novo vs Therapy-Related, and CMML-Specific Cytogenetic Risk Subtypes

OBJECTIVES

We sought to immunophenotype blasts, monocytes, and granulocytes in chronic myelomonocytic leukemias (CMMLs) and compare CMML subtypes, to identify if significant antigen expression differences existed.

METHODS

Bone marrow blasts, monocytes, and granulocytes from CMML subgroups (n = 30; World Health Organization types 1/2, proliferative/dysplastic, therapy related/de novo, and low/intermediate/high cytogenetic risk) were immunophenotypically compared by flow cytometry with 10 nonneoplastic control marrows.

RESULTS

Aberrancies were present in blasts of 26 (87%) of 30 CMMLs (26 diagnostic; four follow-up) and six (60%) of 10 controls (P = .089), monocytes of 28 (93%) of 30 CMMLs and six (60%) of 10 controls (P = .026), and granulocytes of eight (28%) of 29 CMMLs and zero of 10 controls (P = .166). Underexpression of CD14 and CD15 on monocytes was more common in CMMLs compared with controls (P = .008 and P = .043). Statistical analysis showed no significant difference in antigen expression between the CMML subgroups on blasts or monocytes; granulocytes demonstrated more common HLA-DR expression in CMML-2 vs CMML-1.

CONCLUSIONS

These findings confirm heterogeneity within CMML subgroups and find no specific qualitative or quantitative findings characteristic of a subgroup.

Multiparameter flow cytometry is instrumental to distinguish myelodysplastic syndromes from non-neoplastic cytopenias

Mandatory for the diagnosis of myelodysplastic syndromes (MDS) is the presence of dysplasia in >10% of cells within one or more cell lineages or presence of >15% ring sideroblasts or presence of MDS-associated cytogenetic (CG) abnormalities. Discrimination between neo-plastic and non-neoplastic causes of cytopenias can be challenging when dysplastic features by cytomorphology (CM) are minimal and CG abnormalities are absent or non-discriminating from other myeloid neoplastic disorders. This study evaluated a standard diagnostic approach in 379 patients with unexplained cytopenias and highlights the additional value of flow cytometry (FC) in patients with indeterminate CM and CG. CM reached no clear-cut diagnosis in 44% of the patients. Here, CG was able to identify two additional patients with MDS; other CG results did not reveal abnormalities or were not contributory. Based on the FC results, patients without a diagnosis by CM and CG were categorized 'no MDS-related features' (65%), 'limited number of MDS-related changes' (24%), and 'consistent with MDS' (11%). Patients were followed over time in an attempt to establish or confirm a diagnosis (median follow-up 391 d, range 20-1764). The specificity (true negative) of MDS-FC analysis calculated after follow-up was 95%. FC can aid as a valuable tool to exclude MDS when CM and additional CG are not conclusive in patients with cytopenia.

Flow cytometry immunophenotypic findings in chronic myelomonocytic leukemia and its utility in monitoring treatment response

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic/myeloproliferative neoplasm, characterized by persistent monocytosis. Due to the lack of unique surface markers expressed by neoplastic monocytes and the frequent CD34-negative blast immunophenotype, the diagnostic value of flow cytometric immunophenotyping (FCI) in CMML is rarely studied. In this study, by using a multicolor FCI assay, we assessed bone marrow (BM) immunophenotypical alterations in 118 CMML patients and follow-up BM samples in 35 of these patients. The median BM monocytes as determined by FCI were 14% (1-63%), correlated with morphologic count (P = 0.0004). FCI alterations in monocytes were observed in 96% and granulocytes in 83% of cases. The percentage of CD34(+) myeloblasts by FCI was low [median 0.6% (0.02-12.6%)], but exhibiting frequent aberrancies [median 6 (2-12)]. CD34(+) B-cell precursors were absent in 93% of cases. In 35 patients with follow-up BM samples assessed, the CD34(+) myeloblasts showed persistent FCI aberrancies in all 29 patients treated with hypomethylating agents and 3 patients on observation, but became normal in 3 patients following stem cell transplant. In conclusion, CMML exhibit numerous FCI alterations in monocytes, granulocytes, and more profound/frequent in CD34(+) myeloblasts. These findings provide solid evidence for using FCI as an ancillary test in CMML diagnosis and also, in assessment of treatment responses.

Flow cytometry immunophenotypic analysis of Philadelphia-negative myeloproliferative neoplasms: Correlation with histopathologic features

BACKGROUND

Compared with the proven utility of flow cytometry immunophenotyping (FCI) analysis in the workup of myelodysplastic syndromes (MDS), immunophenotypic alterations in myeloproliferative neoplasms (MPN) have been less studied and the potential utility of FCI is not defined.

METHODS

Bone marrow (BM) samples of 83 Philadelphia-negative MPN patients were assessed by multicolor FCI including 27 with essential thrombocythemia (ET); 17 polycythemia vera (PV); 33 primary myelofibrosis (PMF) and 6 MPN-unclassifiable (MPN-U). The time interval from initial diagnosis of MPN to FCI analysis was 18 months (0-370). Ninety-five age-matched MDS patients with a similar BM blast count were included for comparison.

RESULTS

Immunophenotypic alterations, either in CD34(+) cells or myelomonocytic cells, were detected in 82 of 83 (99%) MPN cases. FCI abnormalities were more frequently observed in cases with substantial myelofibrosis but not different between PMF and fibrotic stage of ET/PV. Furthermore, FCI abnormalities were more frequent in cases with ≥5% BM blasts and/or circulating blasts (P = 0.006); as well as cases with an abnormal karyotype (P = 0.036); but not associated with morphologic dysplasia or JAK2 mutation status. Comparing with MDS, FCI abnormalities were overall less pronounced in MPN cases (P = 0.001).

CONCLUSIONS

MPNs exhibit frequent immunophenotypic alterations, more pronounced in cases with adverse histopathologic features. These findings illustrate that immunophenotypic alterations are a part of constellational findings in MPN, and correlate progressively with disease stage. The study results also suggest a role of FCI in diagnosis of MPN and monitoring disease over time and after therapy.

Loss of blast heterogeneity in myelodysplastic syndrome and other chronic myeloid neoplasms

OBJECTIVES

Flow cytometry immunophenotyping has been suggested as an adjunctive technique in the evaluation of myeloid malignancies, especially in the myelodysplastic syndromes. However, its use has been limited due to complexity and cost restraints. The goal of this study is to attempt a simpler approach to flow cytometry immunophenotyping in myeloid neoplasms.

METHODS

We analyzed bone marrow specimens of 45 selected patients and an additional 99 consecutive random patients using a limited antibody panel.

RESULTS

Normal CD34-positive blasts show a characteristic pattern of CD13/HLA-DR expression, with three readily identifiable subpopulations. In contrast, myeloid neoplasms frequently show loss of this heterogeneity.

CONCLUSIONS

Analysis of a limited antibody panel with a focus on CD13/HLA-DR expression provides relatively high specificity and sensitivity for the detection of myeloid neoplasms.

Revisiting guidelines for integration of flow cytometry results in the WHO classification of myelodysplastic syndromes-proposal from the International/European LeukemiaNet Working Group for Flow Cytometry in MDS

Definite progress has been made in the exploration of myelodysplastic syndromes (MDS) by flow cytometry (FCM) since the publication of the World Health Organization 2008 classification of myeloid neoplasms. An international working party initiated within the European LeukemiaNet and extended to include members from Australia, Canada, Japan, Taiwan and the United States has, through several workshops, developed and subsequently published consensus recommendations. The latter deal with preanalytical precautions, and propose small and large panels, which allow evaluating immunophenotypic anomalies and calculating myelodysplasia scores. The current paper provides guidelines that strongly recommend the integration of FCM data with other diagnostic tools in the diagnostic work-up of MDS.

Role of flow cytometry in myelodysplastic syndromes: diagnosis, classification, prognosis and response assessment

Myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid neoplasms. With the emergence of therapeutic options, attempts to standardize diagnostic, prognostic and response criteria to guide treatment decisions are increasingly important. This has been achieved in part by the revised 2008 World Health Organization classification and consensus guidelines outlining refined definitions and standards. Conventional criteria have limitations in terms of sensitivity and specificity. Multiparameter flow cytometry (FC) can be used real-time, and is a highly reproducible and objective way of assessing the pattern of expression of multiple antigens on a single hematopoietic cell and defined subpopulations. By comparing antigen expression within maturing myelomonocytic populations with that identified on the equivalent normal cells, abnormalities identified may provide a diagnostic indication of stem cell dysmaturation. There are now increasingly robust data demonstrating the capacity of FC to discriminate MDS from non-clonal cytopenias and dysplasia, as well as further refine disease classification and prognostication, which will be reviewed here.

GCSF-R expression in myelodysplastic and myeloproliferative disorders and blast dysmaturation in CML

OBJECTIVES

To characterize granulocyte colony-stimulating factor receptor (CD114) expression in normal (n = 20), myelodysplastic (n = 34), and chronic myelogenous leukemia (CML; n = 5) bone marrow by flow cytometry.

METHODS

Clinical bone marrow samples were analyzed using CD33/CD114/CD34/CD117/CD45. CD114 density (mean fluorescence intensity) and cellular distribution were evaluated on early blasts (CD33-), late blasts (CD33+), promyelocytes, and granulocytes.

RESULTS

Normal CD114 acquisition occurred on early blasts, peaked on promyelocytes, and decreased on granulocytes. Forty percent of CD34+ blasts expressed CD114 and one-third were early blasts. In myelodysplastic syndromes, altered CD114 distribution was more informative than density changes. In CML, CD114 density was significantly decreased on early blasts and expression was essentially limited to late blasts. We observed a specific blast dysmaturation pattern in CML involving CD33, CD34, and CD114 that was 83% sensitive and 100% specific in initial diagnosis.

CONCLUSIONS

CD114 provides useful additional detail in phenotypic assessment of hematopoietic precursor maturation.

Diagnostic potential of CD34+ cell antigen expression in myelodysplastic syndromes

The World Health Organization introduced flow cytometry as an additional criterion for diagnosis of myelodysplastic syndromes (MDS). Aberrant antigen expression on bone marrow (BM) blasts may identify "low-grade MDS." This study aimed to examine differences in antigen expression on CD34+ BM cells between patients with MDS and those with secondary cytopenia. BM aspirates of 175 patients with cytopenia were classified as MDS or secondary cytopenia. Expression of stem cell antigens (CD34, CD133), myeloid antigens (CD13, CD33), B-cell antigens (CD19, CD10), growth factor receptors (CD117, CD123), and chemokine receptor (CD184) was examined. Thirty-two normal adults and 49 patients with CD34+ acute myeloid leukemia (AML) were also examined. High percentage of CD34+ cells, CD117 and CD123 overexpression, and abnormal CD45 expression on these cells are the best markers for MDS. These phenotypic aberrancies correlate with number of blasts and degree of dysplasia, and were similar to those in CD34+ AML, thus reflecting the relationship between these disorders.

Rationale for the clinical application of flow cytometry in patients with myelodysplastic syndromes: position paper of an International Consortium and the European LeukemiaNet Working Group

An international working group within the European LeukemiaNet gathered, aiming to determine the role of flow cytometry (FC) in myelodysplastic syndromes (MDS). It was agreed that FC has a substantial application in disease characterization, diagnosis and prognosis. FC may also be useful in predicting treatment responses and monitoring novel and standard therapeutic regimens. In this article the rationale is discussed that flow cytometry should be integrated as a part of diagnostic and prognostic scoring systems in MDS.

Multi-color CD34⁺ progenitor-focused flow cytometric assay in evaluation of myelodysplastic syndromes in patients with post cancer therapy cytopenia

Bone marrow assessment for myelodysplastic syndrome (MDS) in a patient who develops cytopenia(s) following cancer therapy is challenging. With recent advances in multi-color flow cytometry immunophenotypic analysis, a CD34(+) progenitor-focused 7-color assay was developed and tested in this clinical setting. This assay was first performed in 73 MDS patients and 53 non-MDS patients (developmental set). A number of immunophenotypic changes were differentially observed in these two groups. Based on the sensitivity, specificity and reproducibility, a core panel of markers was selected for final assessment that included increased total CD34(+) myeloblasts; decreased stage I hematogones; altered CD45/side scatter; altered expression of CD13, CD33, CD34, CD38, CD117, and CD123; aberrant expression of lymphoid or mature myelomonocytic antigens on CD34(+) myeloblasts; and several marked alterations in maturing myelomonocytic cells. The data were translated into a simplified scoring system which was then used in 120 patients with cytopenia(s) secondary to cancer therapy over a 2-year period (validation set). With a median follow-up of 11 months, this assay demonstrated 89% sensitivity, 94% specificity, and 92% accuracy in establishing or excluding a diagnosis of MDS.

A dissection of the CD45/side scatter "blast gate"

CD45/side scatter (SS) gating is widely used for isolating blasts by flow cytometry (FC). However, other cells contaminate the "blast gate" (BG); CD45/SS gating is thus imprecise, particularly when there are few blasts. We studied the BG contents in 21 myelodysplastic syndromes (MDSs), 14 myeloproliferative neoplasms (MPNs), 7 chronic myelomonocytic leukemias (CMMLs), and 40 nonneoplastic control samples using 4-color FC with cluster analysis. There were no significant differences across groups in the median percentage of BG events represented by blasts (14.7%-22%), granulocytes (23.3%-33.2%), lymphocytes (2.1%-3.2%), and erythroids (1.0%-9.8%). Monocytes were a larger percentage of BG events in CMML (24.2%). Basophils averaged 35.4% of the BG in MPNs. The percentage of blasts within the BG averaged 94.2% in control samples vs 88.2% in MDSs and 80.7% in CMMLs. Blasts averaged about 20% of events in the BG. About 10% to 20% of blasts fell outside the BG in CMMLs and MDSs. Our data highlight pitfalls in using a traditional BG for blast analysis in nonacute myeloid disorders.

Flow cytometry in myelodysplastic syndrome: analysis of diagnostic utility using maturation pattern-based and quantitative approaches

Flow cytometry (FCM) is being increasingly evaluated for the diagnosis of myelodysplastic syndrome (MDS). We employed multiple FCM approaches to assess MDS. Five-color FCM, morphology blind, was done on bone marrow aspirates of 57 suspected MDS and 31 normal controls. Maturation pattern, quantitative FCM for low-grade MDS that awards FCM score, and expression of selected antigens on erythroid cells and CD34(+) blasts were evaluated. FCM results were correlated with clinical and laboratory workup. Patients (n = 57) included proven MDS (n = 14), suspected MDS (n = 13), and non-MDS (n = 30). By pattern-based approach, all proven cases were FCM positive. In suspected MDS, 11 (84.61 %) were positive including morphology-negative cases, and two (15.38 %) were intermediate. In non-MDS cases, 27 of 30 (90 %) were FCM negative, 2 of 30 (6.67 %) intermediate, and 1 of 30 (3.33 %) a hematinic-responsive case, positive. Quantitative parameters that characterized MDS included FCM score of >3, percentage CD34(+) B cells, and expression of CD11b, CD15, and CD56 on myeloblasts. CD71 MFI on CD235a(+) erythroblasts and CD38 MFI on myeloblasts were significantly lower in MDS. The former was present in FCM-intermediate suspected MDS but not FCM-intermediate non-MDS cases. Used in the overall clinical context, both maturation pattern recognition and quantitative approaches, the latter for low-grade MDS, are sensitive methods of diagnosing MDS, including cases negative by morphology and cytogenetics, especially if combined with evaluation of selected antigens, CD71 on CD235a(+) cells and CD38 on CD34(+) cells. The value of FCM in morphology-negative cases needs better definition of specificity through more extensive evaluation of secondary dyspoiesis.

Diagnosis of myelodysplastic syndromes in cytopenic patients

Sustained clinical cytopenia is a frequent laboratory finding in ambulatory and hospitalized patients. For pathologists and hematopathologists who examine the bone marrow (BM), a diagnosis of cytopenia secondary to an infiltrative BM process or acute leukemia can be readily established based on morphologic evaluation and flow cytometry immunophenotyping. However, it can be more challenging to establish a diagnosis of myelodysplastic syndrome (MDS). In this article, the practical approaches for establishing or excluding a diagnosis of MDS (especially low-grade MDS) in patients with clinical cytopenia are discussed along with the current diagnostic recommendations provided by the World Health Organization and the International Working Group for MDS.

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

Flow cytometry (FC) is increasingly recognized as an important tool in the diagnosis and prognosis of myelodysplastic syndromes (MDS). However, validation of current assays and agreement upon the techniques are prerequisites for its widespread acceptance and application in clinical practice. Therefore, a working group was initiated (Amsterdam, 2008) to discuss and propose standards for FC in MDS. In 2009 and 2010, representatives from 23, mainly European, institutes participated in the second and third European LeukemiaNet (ELN) MDS workshops. In the present report, minimal requirements to analyze dysplasia are refined. The proposed core markers should enable a categorization of FC results in cytopenic patients as 'normal', 'suggestive of', or 'diagnostic of' MDS. An FC report should include a description of validated FC abnormalities such as aberrant marker expression on myeloid progenitors and, furthermore, dysgranulopoiesis and/or dysmonocytopoiesis, if at least two abnormalities are evidenced. The working group is dedicated to initiate further studies to establish robust diagnostic and prognostic FC panels in MDS. An ultimate goal is to refine and improve diagnosis and prognostic scoring systems. Finally, the working group stresses that FC should be part of an integrated diagnosis rather than a separate technique.

Role of flow cytometry in diagnostics of myelodysplastic syndromes--beyond the WHO 2008 classification

Multiparameter flow cytometry (FCM) is an excellent method to follow the expression patterns of differentiation antigens using monoclonal antibodies to surface and cytoplasmic proteins. Although several authors described various aberrant immunophenotypic features in the bone marrow of patients with myelodysplastic syndromes (MDS), the World Health Organization 2008 classification recommended that, only if 3 or more phenotypic abnormalities are found involving 1 or more of the myeloid lineages can the aberrant FCM findings be considered suggestive of MDS. In the absence of conclusive morphologic and/or cytogenetic features, FCM abnormalities alone were considered not sufficient to establish MDS diagnosis and further follow-up of the patients was recommended. Review of the literature gives accumulating evidence that FCM has become an important part of the integrated diagnostic work-up of patients with suspected MDS. Several studies have also reported FCM findings significant for prognosis and therapy choice in MDS patients. Technical progress in multicolor FCM and new analysis programs, together with ongoing efforts to standardize the methodology, will make it possible to apply FCM in individual risk assessment and choice of best therapy for MDS patients.

Implementation of flow cytometry in the diagnostic work-up of myelodysplastic syndromes in a multicenter approach: report from the Dutch Working Party on Flow Cytometry in MDS

Flow cytometry (FC) is recognized as an important tool in the diagnosis of myelodysplastic syndromes (MDS) especially when standard criteria fail. A working group within the Dutch Society of Cytometry aimed to implement FC in the diagnostic work-up of MDS. Hereto, guidelines for data acquisition, analysis and interpretation were formulated. Based on discussions on analyses of list mode data files and fresh MDS bone marrow samples and recent literature, the guidelines were modified. Over the years (2005-2011), the concordance between the participating centers increased indicating that the proposed guidelines contributed to a more objective, standardized FC analysis, thereby ratifying the implementation of FC in MDS.

Flow cytometry immunophenotyping for the evaluation of bone marrow dysplasia

The pathological hallmark of myelodysplastic syndromes (MDS) is marrow dysplasia, which represents the basis of the WHO classification of these disorders. This classification provides clinicians with a useful tool for defining the different subtypes of MDS and determining individual prognosis. The WHO proposal has raised some concern regarding minimal diagnostic criteria particularly in patients with normal karyotype without robust morphological markers of dysplasia (such as ring sideroblasts or excess of blasts). Therefore, there is clearly a need to refine the accuracy to detect marrow dysplasia. Flow cytometry (FCM) immunophenotyping has been proposed as a tool to improve the evaluation of marrow dysplasia. Rationale for the application of FCM in the diagnostic work up of MDS is that immunophenotyping is an accurate method for quantitative and qualitative evaluation of hematopoietic cells and that MDS have been found to have abnormal expression of several cellular antigens. To become clinically applicable, FCM analysis should be based on parameters with sufficient specificity and sensitivity, data should be reproducible between different operators and the results should be easily understood by clinicians. In this report, we reviewed the most relevant progresses in detection of marrow dysplasia by FCM in MDS as defined by WHO criteria.

Flow cytometric scoring system as a diagnostic and prognostic tool in myelodysplastic syndromes

The aim of this study is to validate the clinical utility of the flow cytometric scoring system (FCSS), quantifying phenotypic aberrancies in the myelomonocytic lineages, in the diagnosis and prognosis for conventionally treated myelodysplastic syndromes (MDS) patients. The bone marrow samples from 56 consecutive newly diagnosed MDS patients were characterized by the FCSS and compared with findings in 27 non-MDS cytopenic patients. The FCSS scores were significantly higher in patients with MDS than those in the non-MDS control. A flow score of 2 or more allowed for a specificity of 100% with 75% sensitivity in distinguishing these two groups. The FCSS scores correlated directly with validated prognostic systems including WHO classification, International Prognostic Scoring System (IPSS), WHO-adjusted prognostic scoring system (WPSS) and transfusion dependency. The median survival of conventionally treated MDS patients was directly related to FCSS group; severe: 6 months; moderate: 19 months and normal/mild: not reached. The multivariate analyses suggested the FCSS risk categories were an independent prognostic factor after adjustment for sex, age (above or below 70 years), IPSS or WPSS risk categories. These results confirm that quantifying aberrancies in the myelomonocytic lineage by FCSS is useful in MDS diagnosis and extends the prognostic utility for conventionally treated/untreated patients, especially among patients classified within the refractory cytopenia with multilineage dysplasia (RCMD) subgroup.

Phenotypic abnormalities strongly reflect genotype in patients with unexplained cytopenias

BACKGROUND

In patients with unexplained cytopenias, abnormal karyotyping studies can be found with inconclusive light microscopic findings. Multidimensional flow cytometry (FCM) can identify myelomonocytic cells with aberrant phenotypes often not seen by standard morphology.

METHODS

In 431 patients presenting with unexplained cytopenia(s) FCM results were compared to abnormal karyotyping and FISH results recognized as associated with myelodysplastic syndrome (MDS) in the 2008 WHO classification, to assess the degree of and types of phenotypic abnormalities observed using a previously reported flow cytometric scoring system (FCSS). Fluorescence activated cell sorting was also used to identify subpopulations of abnormal maturing myelomonocytic cells that carry the genotypic abnormality.

RESULTS

For marrows with complex (three or more karyotypic abnormalities), two abnormalities, isolated chromosome seven anomalies, del(5q) or del(13q), 100% of cases were positive when using a FCSS cutoff of ≥ 2. Trisomy 8, del(20 q), and minus Y had flow scores ≥ 2 in 72, 60, and 18%, respectively, but in some cases the flow score was high, indicating myeloid dysplasia. Most patients (16/22) with high myeloid progenitor cells (MyPC) (> 20%) also exhibited maturing myeloid cell abnormalities by FCM. Morphology was negative in the maturing myeloid cells in many cases with phenotypically abnormal myeloid cells.

CONCLUSIONS

The high correlation between genotypic and phenotypic abnormalities suggests a possible increased utility of flow cytometry in the diagnosis of patients with unexplained cytopenias and may be useful in future clinical studies and in the classification by the WHO, using the FCSS rather than simple counting of flow cytometric abnormalities.

Diagnosis of Myelodysplastic Syndromes in Cytopenic Patients

Sustained clinical cytopenia is a frequent laboratory finding in ambulatory and hospitalized patients. For pathologists and hematopathologists who examine the bone marrow (BM), a diagnosis of cytopenia secondary to an infiltrative BM process or acute leukemia can be readily established based on morphologic evaluation and flow cytometry immunophenotyping. However, it can be more challenging to establish a diagnosis of myelodysplastic syndrome (MDS). In this article, the practical approaches for establishing or excluding a diagnosis of MDS (especially low-grade MDS) in patients with clinical cytopenia are discussed along with the current diagnostic recommendations provided by the World Health Organization and the International Working Group for MDS.

The specificity of immunophenotypic alterations in blasts in nonacute myeloid disorders

Data regarding flow cytometry (FC) in nonacute myeloid disorders is confounded by variable gating strategies and controls limited to normal bone marrow (BM) samples. Blasts in diagnostic BM samples of myelodysplastic syndromes (MDSs), myeloproliferative neoplasms (MPNs), and chronic myelomonocytic leukemias (CMMLs) were compared with 20 nonneoplastic cytopenias/cytoses (CCs) and negative staging BM samples using 4-color FC. Blasts in 10 of 20 CCs showed immunophenotypic differences vs control samples. Immunophenotypic alterations were identified in 18 of 21 MDSs, 11 of 14 MPNs, and 7 of 7 CMMLs vs control samples and 13 (62%) of 21 MDSs, 7 (50%) of 14 MPNs, and 3 (43%) of 7 CMMLs vs CCs. Neoplastic-specific blast immunophenotypic changes included expression of CD7, CD11b, CD15, CD36, and CD56; CD34 overexpression; HLA-DR variability; lack of CD13 and CD33; underexpression of CD13, CD33, CD45, and HLA-DR; and partial loss of CD13, CD33, CD38, and CD117. In all cases, blasts were CD34+. Several blast immunophenotypic alterations are shared in neoplastic and nonneoplastic BM samples. Approximately 40% to 60% of neoplastic BM samples exhibited aberrancies not seen in reactive BM samples.

Metal-Containing Polystyrene Beads as Standards for Mass Cytometry

We examine the suitability of metal-containing polystyrene beads for the calibration of a mass cytometer instrument, a single particle analyser based on an inductively coupled plasma ion source and a time of flight mass spectrometer. These metal-containing beads are also verified for their use as internal standards for this instrument. These beads were synthesized by multiple-stage dispersion polymerization with acrylic acid as a comonomer. Acrylic acid acts as a ligand to anchor the metal ions within the interior of the beads. Mass cytometry enabled the bead-by-bead measurement of the metal-content and determination of the metal-content distribution. Beads synthesized by dispersion polymerization that involved three stages were shown to have narrower bead-to-bead variation in their lanthanide content than beads synthesized by 2-stage dispersion polymerization. The beads exhibited insignificant release of their lanthanide content to aqueous solutions of different pHs over a period of six months. When mixed with KG1a or U937 cell lines, metal-containing polymer beads were shown not to affect the mass cytometry response to the metal content of element-tagged antibodies specifically attached to these cells.

Diagnostic tools in the indications for allogeneic stem cell transplantation in myelodysplastic syndromes

The rates of allogeneic stem cell transplantation (SCT) to treat the myelodysplastic syndromes (MDS) is continually increasing. However, given the growing arsenal of therapeutic options in parallel to deeper insight into the heterogeneity of this disorder, determining the indications for SCT in MDS remains a difficult task. The International Prognostic Scoring System (IPSS) serves as a guideline for therapeutic decisions, but many aspects (eg, interpretation of rare cytogenetic abnormalities, combinations of chromosomal alterations and/or molecular markers, variant clinical courses within distinct biological subgroups) remain the subject of continuous investigation. In an effort to achieve a more well-differentiated risk categorization, attempts have been made to perform a more detailed cytogenetic categorization, and the use of various fluorescein in situ hybridization (FISH) techniques has improved the description of aberrations. Multicenter initiatives have standardized multiparameter flow cytometry techniques for diagnosis of MDS. In advanced MDS, screening for molecular mutations can identify cases with a high transformation risk. Finally, the new World Health Organization classification system provides a more homogenous morphological categorization of MDS compared with the former French-American-British system. Consequently, in the near future, risk stratification in MDS might incorporate additional diagnostic tools and categorization systems aimed at improving the timing and indication for SCT in this complex disorder.