A New Approach to CD34+ Hematopoietic Progenitor Cell Counting

Background: In the absence of a gold standard for hematopoietic progenitor counting, the intra-laboratory variation between commonly used strategies for progenitor assessment was compared. Methods and Materials: We used a pool of FITC-conjugated monoclonal antibodies (CD14, CD11b) and PE-CD34 to facilitate CD34 counting, excluding CD14+/CD11b+ bright cells. We compared this protocol with other common methodologies, such as the single-staining approach, known as the Milan method, and the ISHAGE multiparameter method. Results: We show that the CD14/CD11b protocol is a valid approach to progenitor cell counting. Though different methods give different results for progenitor cell counting, Lin's coefficient shows high concordance among flow cytometry counts but a substantial difference with colony- forming unit counts. Both the ISHAGE and CD14/CD11b protocol give higher counts than the Milan method. Moreover, on revising the ISHAGE analysis, we described a rare population of cells with the CD34+CD45neg phenotype, which could have an impact in CD34 counting. Conclusions: We have designed a valid alternative approach for hematopoietic progenitor cell counting, and we show that different methods give different results.