[Myelodysplastic syndromes].

entire chromosome complement to detect numerical as well as structural aberrations. Most chromosomal aberrations in MDS can also be detected by fluorescence in situ hybridization (FISH) analyses, but only pre-defined anomalies can be covered, if a distinct informative probe is used. The IPSS/-R is based on chromosome banding analyses in primary untreated MDS patients. If a bone marrow aspiration is impossible or unsuccessful, e.g. because of dry marrow without liquid BM blood, a lack of informative karyotyping because of metaphases failure or the patient ́s refusal (5%-20%), a reliable karyotyping and thus an adequate cytogenetic risk classification, and, finally, assessment of IPSS/-R risk groups are not possible. In two previous studies, we had compared the results of FISH analyses of enriched CD34, unselected peripheral and bone marrow blood with the results of 379 chromosome banding analyses of bone marrow metaphases performed simultaneously in 360 MDS patients (including follow-up data). We were able to demonstrate that FISH analyses of circulating CD34 progenitor cells from peripheral blood with extended probe panels correlate significantly (P<0.01) with the banding results, and that this method provides valid molecular-cytogenetic information from peripheral blood. Furthermore, we were able to show that the enrichment step is indispensable, because otherwise the clone size measured from unselected peripheral blood is too small and too close to the probe ́s cut-off value to allow valid analyses, and thus a relevant portion of smaller abnormal clones may be missed. Hence, CD34PB FISH is a reliable method for cytogenetic monitoring in untreated and treated, lowand high-risk MDS patients that is not dependent on specific cytogenetic subgroups. To answer the question as to whether the IPSS/-R also works with CD34PB FISH data, we analyzed 328 MDS patients from our prospective multicenter German diagnostic study (clinicaltrials.gov identifier:01355913) by CD34PB FISH at the time of study entry, and compared the results with chromosome banding analyses of 2902 previously published MDS patients of the GermanAustrian, Spanish Hematological Cytogenetic Working Group, IMRAW and IWCG databases. This cohort was chosen for correlation because the number of simultaneous CBA and CD34PB FISH analyses at the time of the CD34 FISH-study entry was too small to allow valid statistical analyses.