Alternative Technologies and Automation in Blood Banking PDF

Chapter 14 **Alternative Technologies and Automation in the Routine Blood Bank** **Gel Technology** The gel test is performed in a specially designed microtube. It is based on the controlled centrifugation of RBCs through a dextran-acrylamide gel. The gel particles are porous and they serve as a...

Chapter 14 **Alternative Technologies and Automation in the Routine Blood Bank** **Gel Technology** The gel test is performed in a specially designed microtube. It is based on the controlled centrifugation of RBCs through a dextran-acrylamide gel. The gel particles are porous and they serve as a reaction medium and filter, sieving the RBC agglutinates according to size during centrifugation. Agglutinated RBCs remain fixed or suspended in the gel, while unagglutinated RBCs travel unimpeded through the length of the microtube, forming a pellet at the bottom following centrifugation. Agglutination reaction in the gel test are graded from 1+ to 4+ as well as negative and mixed field. One of the major advantages of the gel technology is standardization. The gel technique is also stable where washing and control cells for AHG is no longer necessary, also using small amount of sample. The disadvantages of Gel technique are need special incubator, centrifuges and specific pipettes and it has long centrifugation time. **Solid-Phase Technology** The principle of Solid-Phase immunoassay to red blood cell typing and antibody screening test is based on solid-phase red cell adherence technology (SPRCA). The solid-phase technology is currently approved for testing antibody screening, identification and compatibility testing. The microplate test wells in which intact reagent RBCs are bound to microwells, patient\'s serum or plasma and low ionic strength saline (LISS) are added to the RBC-coated microwells, after incubation the mixer the wash step apply to remove excess amount of unbound Ig, anti -- IgG -- coated RBCs is added, the microwells are centrifuged, the positive tests show adherence of indicator RBCs to part or all the well bottom, depending on the strength of reaction. The solid-phase advantages are standard and provide stable and well-defined end points, it is easy to use, and there are no pre dilution of reagent required also the hemolyzed, lipemic or icteric samples can be processed, there is indicator for adding sample. The disadvantages of solid-phase technique is the need for special equipments, centrifuge, incubator and a light source for reading the final result, as well as the increased sensitivity since it detects the weak autoantibodies missing other antibodies. **Comparison of Technologies** +-----------------+-----------------+-----------------+-----------------+ | Routine Blood | | | | | Bank Testing: | | | | | Comparison of | | | | | Traditional and | | | | | Alternative | | | | | Methods | | | | +=================+=================+=================+=================+ | | Traditional | Gel | Solid-Phase | +-----------------+-----------------+-----------------+-----------------+ | Reaction | Tube | Microtube card | Microplate | | chamber | | | wells | +-----------------+-----------------+-----------------+-----------------+ | Reaction | Agglutination | Agglutination | Solid-phase | | patterns | | | immune | | | | | adherence | +-----------------+-----------------+-----------------+-----------------+ | Reaction matrix | None (cells and | Immunologically | Chemically | | | serum/plasma) | inert | modified | | | | dextran-acrylam | polystyrene | | | | ide | microplate | | | | gels | wells | +-----------------+-----------------+-----------------+-----------------+ | Testing | AHG (antihuman | AHG (antihuman | Anti-IgG coated | | detection | globulin sera) | globulin sera) | red cells | +-----------------+-----------------+-----------------+-----------------+ | Washing | Yes | No | Yes | | required | | | | +-----------------+-----------------+-----------------+-----------------+ | Centrifugation | Yes | Yes | Yes | | required | | | | +-----------------+-----------------+-----------------+-----------------+ | Reaction | Quantitative: | Quantitative: | Semiquantitativ | | readings | | | e: | | | 1+ to 4+, MF | 1+ to 4+, MF | strong pos, | | | | | pos, neg, no MF | +-----------------+-----------------+-----------------+-----------------+ | Stable | No | Yes (2 -- 3 | Yes (2 days) | | reactions | | days) | | +-----------------+-----------------+-----------------+-----------------+ | Quality control | Positive and | Lot number of | LISS color | | | negative | cards and | change, pos and | | | controls/ | diluent on day | neg control | | | Coomb\'s check | of use | | | | cells | | | +-----------------+-----------------+-----------------+-----------------+ | Special | No | Yes | Yes | | equipment | | | | +-----------------+-----------------+-----------------+-----------------+ | Automation | No | Yes | Yes | | | | | | | (FDA-approved) | | | | +-----------------+-----------------+-----------------+-----------------+ MF = Mixed field. **Automation** Automated equipments provide a partial solution to personnel shortages and turn around requirements. Automated equipments also provide the level of quality assurance required by new regulatory standards. Barcoding and standardized techniques reduce testing errors. **SUMMARY CHART** - The goal of every blood bank laboratory is to provide quality service and safe blood products. - All blood bank laboratory operations are regulated by law. - Personnel employed by blood bank laboratories must be qualified by education, training, or experience. - A primary source of operational information is the SOP manual. - Hemapheresis is a process that uses an apheresis machine to selectively remove components from donor blood. - Blood and blood components must be stored and shipped under conditions that ensure their viability. - Every donor unit is tested to determine ABO group and Rh type, including weak D when indicated. Units are also tested for selected viral markers. - The type of Rh-negative units must be confirmed because of potential sensitization that may occur if Rh-positive blood is transfused to an Rh-negative recipient. - Manual tube procedures are being replaced by emerging technologies, including gel-based methods and automation. - The advantages of gel and solid-phase technologies over routine tube testing are: - Standardization: There is no tube shaking or resuspension of an RBC button to cause subjectivity in the interpretation of the test. - Stability: There are well-defined endpoints of the reaction. - Decreased sample volume needed for testing - Enhanced sensitivity and specificity - Gel test points to remember: - The principle of the gel test is hemagglutination. - In the gel test, RBCs and serum or plasma are allowed to incubate together in a reaction chamber. - Following incubation, controlled centrifugation drives the RBCs through a specially designed microtube filled with beads of dextran-acrylamide gel. - Agglutinated cells remain at the top of the tube or are trapped in the gel, depending on the size of the agglutinates. - Unagglutinated cells move through the gel to the bottom of the tube. - The gel test reactions are stable for observation or review for 2 to 3 days. - Gel technology is currently approved for ABO forward and reverse grouping, Rh typing, DAT, antibody screening, antibody identification, and compatibility testing. - The major disadvantage of the gel technology is the need to purchase special equipment: a centrifuge to accommodate the microtube cards used for testing and a pipette for dispensing plasma or serum and RBC suspensions into the reaction chambers of the microtubes. - SPRCA assay points to remember: - The principle of SPRCA is based on solid-phase technology. - In SPRCA tests, the target antigen is affixed to the bottom of the microplate wells. - If the test plasma contains antibodies to the antigen, they attach to the fixed antigen, and indicator cells detect the attached antibodies by forming a monolayer of RBCs. - If the test plasma contains no antibodies to the antigen, there is no attachment to the fixed antigen, and the indicator cells form a clearly delineated button at the center of the microplate well. - Solid-phase reactions are stable for observation or review for 2 days. - Solid-phase technology is currently approved for antibody screening, antibody identification, and compatibility testing. - Advantages of solid-phase technology include the ease of use, because no predilution of reagents is required, and the ability to test hemolyzed, lipemic, or icteric samples. Enhanced sensitivity increases the detection of weak alloantibodies. - The major disadvantage of solid-phase technology is the need to purchase special equipment: a centrifuge that can spin microplates, a 37°C incubator for microplates, and a light source for reading the final results. - Solid-phase protein A technology points to remember: - IgG antibodies are captured in microwells that are coated with protein A. - Solidscreen II, which uses solid-phase protein A technology, is an assay that uses traditional antiglobulin technique. - Solid-phase protein A testing is available only in the United States as an automated technology on the TANGO optimo instrument. - Solid-phase immunosorbent assay (ELISA) points to remember: - The MACE products provide well-characterized monoclonal antibodies immobilized in microwells that are used to capture glycoproteins from platelets supplied by the user. - MACE is used primarily for compatibility testing. - The PAK products provide well-characterized platelet glycoproteins that are either immobilized directly or captured by monoclonal antibodies to wells of a microwell plate. - PAK is used to detect and differentiate between antibodies that bind to platelet-specific glycoproteins (IIb/IIIa, Ib/IX, Ia/IIa, and IV) and class I HLA, primarily for compatibility testing. - Luminex-based assay points to remember: - Luminex-based assay is a bead-based assay that uses florescence and flow cytometry to test for platelet/HLA antibodies. - Luminex assay uses a mixture of 100 different colored beads, each bead coated with a different protein. - The flow cytometer distinguishes between each of the 100 beads by the amount and color of the internal dyes.