When performing Lot Verification on Blood Bank reagents, what is the lowest agglutination strength deemed acceptable when establishing acceptance criteria for a new lot? We are leaning on 2+ or greater.

Alex

Before you set a specific number across the board, I would suggest that you check you package inserts. Some of the human source rare antisera have positive agglutination defined as 2+ or greater and don't usually give much stronger reactions. The monoclonal rare antisera usually seems to react 3-4+.  I would also expect stronger reactivity for anti-A or anti-B, depending on what you are testing them against. I would see 2+ reactivity for them as an indication that the reagent is not OK. We look for reactivity consistent w/ previous lots - +/- one grade of agglutination.