Reproducibility of the World Health Organization 2008 criteria for myelodysplastic syndromes.

The reproducibility of the World Health Organization 2008 classification for myelodysplastic syndromes is uncertain and its assessment was the major aim of this study. The different peripheral blood and bone marrow variables required for an adequate morphological classification were blindly evaluated by four cytomorphologists in samples from 50 patients with myelodysplastic syndromes. The degree of agreement among observers was calculated using intraclass correlation coefficient and the generalized kappa statistic for multiple raters. The degree of agreement for the percentages of blasts in bone marrow and peripheral blood, ring sideroblasts in bone marrow, and erythroid, granulocytic and megakaryocytic dysplastic cells was strong (P<0.001 in all instances). After stratifying the percentages according to the categories required for the assignment of World Health Organization subtypes, the degree of agreement was not statistically significant for cases with 5-9% blasts in bone marrow (P=0.07), 0.1-1% blasts in peripheral blood (P=0.47), or percentage of erythroid dysplastic cells (P=0.49). Finally, the interobserver concordance for World Health Organization-defined subtypes showed a moderate overall agreement (P<0.001), the reproducibility being lower for cases with refractory anemia with excess of blasts type 1 (P=0.05) and refractory anemia with ring sideroblasts (P=0.09). In conclusion, the reproducibility of the World Health Organization 2008 classification for myelodysplastic syndromes is acceptable but the defining criteria for blast cells and features of erythroid dysplasia need to be refined.