Conclusions of a national multicenter intercomparative study of in vitro cultures of human hematopoietic progenitors

With the aim of developing a standardized program of clonogenic cultures, a multicenter intercomparative study of human CFU-GM, BFU-E and CFU-GEMM cul tures was conducted. Aliquots of fresh mononuclear cord blood cells, as wel l as uniform culture materials and instructions for cell culture and for co lony scoring were distributed to 28 national laboratories involved in hemat opoietic research and transplantation. High interlaboratory coefficients of variation (CV) in the reported number of progenitors were found in our fir st intercomparative study (range 67-231%), To investigate the relevance of colony scoring in variations of the reported colony numbers, participants w ere invited to attend a meeting where a single culture dish was scored. In this case, the CVs ranged from 31% to 81%, A subsequent intercomparative as say was then conducted, and significant reductions in the inter-laboratory CVs were obtained with respect to the first study (CVs for colonies grown w ith two different media: CFU-GMs, 48% and 55%; BFU-Es, 70% and 62%; CFU-GEM Ms, 70% and 51%; respectively). In most instances CVs were not significantl y different from those obtained in the single plate scoring study, suggesti ng that the scoring process was the most relevant parameter accounting for variations in the reported colony numbers.