When multiple antibodies are present, which antigen should be typed for first? Besides typing with commercial antisera, are there other ways to screen donors?

The most efficient strategy is to type for the antigen with the highest frequency first. For example, for a patient with anti-e and anti-K, type for the e antigen first (frequency of 98%) compared to K (frequency of 9%).

If it will be difficult to find antigen-negative donors (multiple antibodies or an antibody to a high frequency antigen)--and if there is ample patient serum/plasma containing detectable antibody -- consider first screening donors using patient plasma. Then antigen type the plasma-compatible donors using commercial antisera.