The invention relates to a novel analysis process based on a simple or complex agglutination reaction, inter alia for blood analysis, more particularly but not exclusively for blood groupings, and to a novel apparatus for carrying the process into practice.
The known methods, most of which are either manual or part-automatic, use vessels (cavities) in which the reactions proceed. The vessels are either individual or grouped on a flat support. They are usually made of glass or plastics.
The vessels are usually of cylindrical shape and have either conical or spherical ends; they are of course open at the top so that they may be filled. Also, so that vessels grouped on a plate may be produced, the vessel axes must be parallel to one another.
In the case of grouped vessels, the same are disposed in rows in a perpendicular arrangement - i.e., they ae distributed in a rectangular or square shape on their support.
In endeavors to save on reagents, which are often costly, the tendency is to reduce vessel dimensions and therefore the dimensions of the support plates.
However, when a large number of vessels, even small vessels, are arranged on a support, it is impossible to arrange for centrifuging such that the axis of each vessel is completely coaxial with the direction of the centrifuging force, since the vessels are disposed in parallel relationship to one another. The only way of complying with such a condition is for the centrifuge to be of infinite radius. Consequently, agglutination after centrifuging for any given kind of reaction is not the same for each vessel. Some of the globules remain free in some vessels since such globules have been displaced on to the cone surface, and not its apex, by the centrifugal force.
As a check on the nature and quality of the reaction, the globules must be returned to the suspended state after centrifuging, to which end the plate is given a vibratory treatment for varying lengths of time. Interpretation of results is baaed on observation and estimation of the relative quantities of globules which have agglutinated and of globules which have remained in suspension. The estimation is made all the more difficult in that, when a large number of vessels are disposed on a support, the phenomenon of agglutination during centrifuging may be different in all of the vessels on the plate, for the reasons just mentioned.