The current World Health Organization classification of myelodysplastic syndromes is based morphological evaluation of bone marrow dysplasia. In clinical practice, the reproducibility of the ...recognition of dysplasia is usually poor especially in cases that lack specific markers such as ring sideroblasts and clonal cytogenetic abnormalities.
We aimed to develop and validate a flow cytometric score for the diagnosis of myelodysplastic syndrome. Four reproducible parameters were analyzed: CD34(+) myeloblast-related and B-progenitor-related cluster size (defined by CD45 expression and side scatter characteristics CD34(+) marrow cells), myeloblast CD45 expression and granulocyte side scatter value. The study comprised a "learning cohort" (n=538) to define the score and a "validation cohort" (n=259) to confirm its diagnostic value.
With respect to non-clonal cytopenias, patients with myelodysplastic syndrome had increased myeloblast-related cluster size, decreased B-progenitor-related cluster size, aberrant CD45 expression and reduced granulocyte side scatter (P<0.001). To define the flow cytometric score, these four parameters were combined in a regression model and the weight for each variable was estimated based on coefficients from that model. In the learning cohort a correct diagnosis of myelodysplastic syndrome was formulated in 198/281 cases (sensitivity 70%), while 18 false-positive results were noted among 257 controls (specificity 93%). Sixty-five percent of patients without specific markers of dysplasia (ring sideroblasts and clonal cytogenetic abnormalities) were correctly classified. A high value of the flow cytometric score was associated with multilineage dysplasia (P=0.001), transfusion dependency (P=0.02), and poor-risk cytogenetics (P=0.04). The sensitivity and specificity in the validation cohort (69% and 92%, respectively) were comparable to those in the learning cohort. The likelihood ratio of the flow cytometric score was 10.
A flow cytometric score may help to establish the diagnosis of myelodysplastic syndrome, especially when morphology and cytogenetics are indeterminate.
1 Division of Hematology, Department of Medicine, Nippon Medical School, Tokyo, Japan
2 Department of Hematology Oncology, University of Pavia Medical School and Fondazione IRCCS Policlinico San ...Matteo, Pavia, Italy
3 Division of Hematology, Department of Internal Medicine, Chiba Hokusoh Hospital, Nippon Medical School, Chiba, Japan
4 Department of Hematology, Saitama I nternational Medical Center, Saitama Medical University, Saitama, Japan
5 Department of Industrial Science and Technology, Tokyo University of Science, Chiba, Japan
6 First Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Fukuoka, Japan
Correspondence: Kiyoyuki Ogata, Division of Hematology, Nippon Medical School, 1-1-5 Sendagi, Bunkyoku, Tokyo 113-8603, Japan. E-mail: ogata{at}nms.ac.jp
Background: The diagnosis of myelodysplastic syndromes is not always straightforward when patients lack specific diagnostic markers, such as blast excess, karyotype abnormality, and ringed sideroblasts.
Design and Methods: We designed a flow cytometry protocol applicable in many laboratories and verified its diagnostic utility in patients without those diagnostic markers. The cardinal parameters, analyzable from one cell aliquot, were myeloblasts (%), B-cell progenitors (%), myeloblast CD45 expression, and channel number of side scatter where the maximum number of granulocytes occurs. The adjunctive parameters were CD11b, CD15, and CD56 expression (%) on myeloblasts. Marrow samples from 106 control patients with cytopenia and 134 low-grade myelodysplastic syndromes patients, including 81 lacking both ringed sideroblasts and cytogenetic aberrations, were prospectively analyzed in Japan and Italy.
Results: Data outside the predetermined reference range in 2 or more parameters (multiple abnormalities) were common in myelodysplastic syndromes patients. In those lacking ringed sideroblasts and cytogenetic aberrations, multiple abnormalities were observed in 8/26 Japanese (30.8%) and 37/55 Italians (67.3%) when the cardinal parameters alone were considered, and in 17/26 Japanese (65.4%) and 42/47 Italians (89.4%) when all parameters were taken into account. Multiple abnormalities were rare in controls. When data from all parameters were used, the diagnostic sensitivities were 65% and 89%, specificities were 98% and 90%, and likelihood ratios were 28.1 and 8.5 for the Japanese and Italian cohorts, respectively.
Conclusions: This protocol can be used in the diagnostic work-up of low-grade myelodysplastic syndromes patients who lack specific diagnostic markers, although further improvement in diagnostic power is desirable.
Key words: myelodysplastic syndromes, flow cytometry, diagnosis.
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