The International Prognostic Scoring System (IPSS) was created for evaluating clinical outcomes of patients with myelodysplastic syndromes (MDS). We evaluated the depth of cytopenias to determine whether this parameter could further refine the prognostic ability of the IPSS. Correlation was determined between the depth of cytopenias in 816 patients from the International MDS Risk Analysis Workshop database and patients' clinical features. Univariate analyses of hemoglobin (Hb), absolute neutrophil count, and platelet depth levels were assessed relative to the IPSS risk groups, refined French-American-British categories, cytogenetic groups, bone marrow blast percentage (%), age groups, overall survival (OS), and time to evolution of acute myeloid leukemia (AML). Multivariate analysis of different cytopenic levels was performed to determine whether depth of cytopenias was prognostically additive to the IPSS. All cytopenic categories had statistically significant rank correlations with IPSS, bone marrow blast %, and refined French-American-British categories. In multivariate analysis, Hb levels had additive prognostic value to the IPSS for evaluation of OS, but not time to AML, with greatest prognostic value in Intermediate-1 and Intermediate-2 categories. In contrast, platelet or absolute neutrophil count levels alone or in combination lacked additive prognostic value to the IPSS regarding OS or time to AML evolution. The depth of Hb level per se at the time of diagnosis has additive predictive value to the IPSS for OS in the intermediate-risk groups. This information should prove useful for aiding therapeutic decision-making, prognostic classification, and designing clinical trials for patients with MDS. Am. J. Hematol. 83:765-770, 2008. V