(P-TS-13) Antibody Detection Using Manual Gel Method: Is All Gel the Same?

Using gel techniques to detect and identify antibodies to red cell antigens is a reliable method widely employed in blood banks. However, our immunohematology reference laboratory noticed variability in antibody detection among different gel manufacturers in some patient samples referred to us by our clients. When positive antibody screens detected using one gel system couldn't be replicated using another, we initiated an investigation into the differences between gel manufacturers.

Study

Design/Methods:

We designed a manual gel antibody detection correlation study between three manufacturers (QuidelOrtho, Bio-Rad and Grifols) using 22 samples with known antibodies to red cell antigens. These included 17 alloantibodies from 15 different patients and 7 additional patients with positive antibody screens due to anti-CD38 monoclonal antibody treatment. Samples were tested using the manufacturers’ anti-IgG gel cards, red cell reagents and diluents. The equipment was provided by Grifols and QuidelOrtho and used as per manufacturer’s directions. The Bio-Rad equipment was not available at the time of the study, so the QuidelOrtho equipment was substituted. Antibody screens were incubated at 37⁰C for 15 minutes and centrifuged for 10 minutes. Samples from patients with an antibody due to anti-CD38 monoclonal antibody therapy were tested against DTT (0.2M) treated reagent red blood cells (2-4%) from a separate vendor (Werfen) that were diluted to 0.6-1.0%.

Results/Findings:

Seven of the antibodies tested reacted the same in all 3 gel systems. The additional 10 antibodies tested reacted differently in all 3 gel systems. See Table 1. The samples with anti-CD38 had negative antibody screens as expected when tested with DTT treated red blood cells using the QuidelOrtho and Bio-Rad anti-IgG gel cards (one patient demonstrated an underlying anti-Jk^a) whereas the Grifols anti-IgG cards displayed inconclusive results.

Conclusions:

Antibodies to red cell antigens of strength 2+ or greater react consistently across gel systems. Weaker antibodies exhibit variability. DTT-treated red blood cells react as expected with Ortho and Bio-Rad systems but are inconclusive with Grifols. Variability exists in detecting and identifying antibodies to red cell antigens among gel manufacturers.