REPORT ON INITIAL EXPERIENCES GAINED ON E STABLISHING A REGIONAL MULTICENTER EVALUATION OF LYMPHOCYTE SUBTYPING BY FLOW-CYTOMETRY

Participation in a multicenter evaluation of flowcytometric investigat ions is the only possibility of providing external quality control. Up to now nine different laboratories have taken part in this program, m easuring two samples of fresh EDTA blood according to a recommended an tibody panel. The choice of antibodies was intended to reach a standar dized immune status. Three different types of flowcytometers were used . All results were expressed in lymphocyte subset percentages and in a bsolute values. The coefficient of variation of each lymphocyte subpop ulation was used for interpretation of the results of all working grou ps, as well as the control measurement. The results of the control mea surement already showed that there was a difference between the obtain able coefficient of variation for the different subpopulations. In the case of CD3, CD4 and CD8 positive lymphocytes the relative percentage s of the total group gave values far below 10%. The coefficients of va riation of the activated T-lymphocytes or the cytotoxic T-cells, as we ll as of the absolute values were definitely higher. Already after the second multicenter evaluation the achieved results showed positive as pects such as improvements of the outcome, advancement of the user con tacts, cooperation and impulses by discussing interesting problems.