[Quantitative measurement of red cell antigens with Groupamatic]

Groupamatic 360 can be adapted to the quantitative measurement of erythrocyte agglutination reactions. Here the authors give the necessary conditions to obtain the best sensitivity and the best reproductibility. They have considered globular suspensions, incubation of the erythrocyte antiserums mixtures, centrifugation, agitation, photometric measurement. As concerns the quantitative technique, we used the average peripheral measurement obtained in the twleve cuvettes of the same selected disc sector. The calibration is fixed to 50 mV for a non agglutinated red cell suspension and to 950 mV for albumin in a saline solution. In these conditions, the best discrimination is obtained for agglutination with measures between 400 and 800 mV. The maximum sensitivity is reached with reactions corresponding to 600 mV, that is to say in our selected conditions with 50% of free red cells. The choice of the zone between 500 and 600 mV enables to detect variations from 1.5 to 2% in an antibody solution concentration. This zone is particularly favorable for quantitative work. Although a part of these operations in this preliminary work were manually effected, the automatic centrifugation, agitation, photometric measurement and results print out make possible a large number of measurements with very satisfactory reproductibility conditions. Besides, these experiments pointed out some factors of improvement which will be helpful for the new 360 G Groupmatic equipments.