Cytofluorimetric analysis of CD34 cells.

The cytofluorimetric enumeration of CD34-positive cells is a useful method for measuring haematopoietic stem cells. The large variation of results between different laboratories, in multicenter quality control studies, could be due to multiple technical problems. CD34 analysis must be performed in whole blood and the NH4Cl or the NH4Cl-derived reagents give the best results in the lysis procedure. The monoclonal antibody for CD34 detection must be a class III, if possible PE-conjugated. Any differences were found in the absolute CD34 count using different analysis protocols: Milan, ISHAGE, Dutch, or a commercial kit, when the sample is fresh and in good viable condition. The multiparametric approach, using three or four colours simultaneously, could be required in scoring apheresis products from patients with CD34-positive blast cells (ie ALL of B cell origin) and in deciding the optimum time to start the leukapheresis, choosing, with an equal CD34 number, the moment at which the highest number of more immature progenitor cells (CD38-negative or dim, CD90-positive) is present.