Solid phase testing uses microplates for testing verses gel cards. Solid phase testing occurs in one of the small 96 microwells of the plate. Antigens are bound to the bottom of the plate well with gelatin. Patient’s plasma or serum antibody may attach to the antigen after incubation. The incubated microplate is tested with AHG coated indicator cells for positive reaction observation.
Solid phase testing is done almost exclusively using an automated system. Manual solid phase testing requires special insert adapters for a centrifuge. They require a closed incubator systems with doors. The main reason why automated systems are used is that most technologist find observing and grading them is harder.
The automated solid phase system may be preferred by technologist over gel for a number of reasons. Solid phase requires less serum for testing in most instances. Solid phase is less pron to room temperature antigens and possibly cold agglutinates. Panagglutination may be present in both methodologies.
The gel system is preferred by many technologist. One of the main advantages of this system is the ability to read the cards manually if needed. The gel system also reacts with room temperature antibodies. Many labs consider room temperature antibodies clinical insignificant; but some labs like to evaluate all phases.
Both gel and solid phase systems are limited by their antigens profiles or donor profiles. Gel and solid phase companies are limited by what donors they can recruit. Often these donors are paid or highly recruited to complete the antigrams. These companies make antigrams that are able to rule out certain suspected antibodies. These antigrams may not be tailored to screening certain populations. For example: Donors may be recruited for antigrams in Boston. The antigrams made from these donors may not be well suited for the sickle cell population.
In conclusion a technologist must consider many factors when deciding on a testing platform.
