Background/Case Studies: Blood donors who have history of pregnancy or transfusion may develop Red Blood Cell (RBC) antibodies (Ab) as a result of sensitization. Antibody screen (ABS) is routinely performed on donor blood for detection of RBC Ab. A small percentage of donors may test positive for Ab, and present with a positive ABS. This testing may be performed by automated or manual methods. Tube method (TM) limits efficiency and testing output. The tube capacity in cell washers can often accommodate no more than 24 tubes per rotor, which is the equivalent to 8 donors per test run. When reading test results on 24 tubes, reaction strength weakens with time. Wait time in centrifuge can result in false negative reactions. Microcolumn agglutination (gel) testing has the capacity to screen the equivalent of 2 donors per card. Centrifuge capacity is 24 donors per run. Microplate (MCP) testing does not require reagent volumes as described in TM. Reagents are diluted to microvolumes to screen up to 32 donors per run.
Study
Design/Methods: MCP ABS was compared to TM using enhancement with Polyethylene Glycol (PeG). 60 donor tubes tested in parallel with TM. 26 with positive ABS and 34 with negative ABS. Donor Ab specificity was determined using TM. Ab specificity and number included in the validation were: D-4, C-2, E-5, c-1, e-1, K-6, Fya-3, Jka-1, S-2, and multiple ab: E/K-1. TM was performed using a 3 cell ABS, 2 drops PeG incubated at 37°C for 15 minutes, washed x3 with 0.85% normal saline (NS), results read at antihuman globulin phase (AHG) using Anti-IgG. All negative reactions were confirmed using coombs check cells. MCP testing was performed using the following: a 96 well plate, donor-sourced EDTA plasma, diluted 3 cell ABS (diluted 1 part 0.85% NS / 2 parts ABS cells). Micropipettes were used to deliver neat PeG to the MCP. MCPs were sealed with polyethylene sheets prior to dry incubation at 37°C for 30 to 60 minutes to prevent dehydration. After incubation, MCP tests were washed 4x manually with 0.85% NS. Diluted Anti-IgG (1:2 / 0.85% NS) was used to detect in-vitro sensitization at AHG. Incubation time and centrifuge RPM were adjusted during the validation to obtain optimal results.
Results/Findings: Interpretation of overall test results for both methods were interpreted as positive or negative. MCP results were 100% reproducible to TM. Negative tests form a drip pattern, positive tests appear as a button (Figure A). Conclusions: MCP testing reduces reagent usage, increases productivity, and decreases technical time. MCP results are easily read macroscopically.
