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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Use of a Blast Dominance-Hematogone Index for the Flow Cytometric Evaluation of Myelodysplastic Syndrome (MDS)

OBJECTIVES

We tested whether combined flow cytometric assessment of loss of blast heterogeneity and decreased hematogones is a diagnostically useful approach for evaluation of myelodysplastic syndrome (MDS).

METHODS

Bone marrow samples from patients with known MDS were analyzed by 10-color flow cytometric immunophenotyping and compared with normal bone marrow samples.

RESULTS

There was loss of blast heterogeneity in patients with MDS compared with normal bone marrow samples, based on the relative size of the dominant blast population (83.0% vs 64.8%) and fewer hematogones (0.08% vs 1.39%). The size of the largest blast population divided by the fraction of hematogones (blast dominance-hematogone [BDH] index) was significantly larger in MDS compared with normal cases (27,084 vs 190, P < .0001; receiver operating characteristic area under the curve = 0.96).

CONCLUSIONS

The BDH index is more sensitive and specific than loss of blast heterogeneity or decrease in hematogones for detecting MDS in bone marrow samples and may be useful in clinical practice.

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.

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.