Currently known column blood-typing systems, including, for example, the AutoVue systems manufactured by Ortho Clinical Diagnostics Inc., of Raritan, N.J., among others, were originally optimized for manual testing. As a consequence, a number of characteristics of the systems, while supporting the manual determination of a positive reaction, do not support facile automation.
First, agglutination strength is determined in a manner that is optimized for a subjective visual read. This determination is based upon a perceived distribution of red color from red blood cells, RBCs, in an elongated column, with an agglutinated sample being characterized by red color that is distributed above the bottom of the column, with a non-agglutinated sample having red color localized at the bottom thereof.
Automated reading of the distribution of red color is complex and requires a vision system that is coupled with relatively sophisticated software algorithms in order to appropriately classify the wide range of color distribution patterns that can be encountered. Such a technique is described, for example, in U.S. Pat. Nos. 5,594,808 and 5,768,407.
In these systems, a centrifugation step of relatively long duration (e.g., approximately 15 or 20 minutes) is typically required in order to achieve a necessary spatial separation of the agglutinated from the unagglutinated cells, including both incubation and centrifugation times.
Analysis of agglutination patterns however, is often an urgent procedure, for example in the case of injury, and the elimination of time in the blood typing process is therefore highly significant and greatly desired in the field.
A technique that permits agglutination to be detected without centrifugation has been more recently described by Applicants' in U.S. Pat. No. 7,452,508 and U.S. Patent Publication No. US 2002/0081747, each of which is incorporated by reference in its entirety. This technique defines apparatus and a method for aspirating within a probe tip and is defined such that most of the liquid diameters of the tip to cause rotational mixing of the liquid. This method is useful in providing agglutination of blood, which can then in turn be used in blood typing. The classification and determination of agglutination strength, however, regardless of the technique used to cause separation, is the same as described above, e.g., thereby requiring spatial separation of the agglutinated/unagglutinated cells.