Our facility is evaluating making a change to our process for Weak D testing for patients with a positive DAT. For years, if we were required to do a Weak D, but the patient had a positive DAT, we used to cancel the Weak D as invalid. Another hospital in our system mentioned that they tended to perform the Weak D, but then only cancel as invalid if the Weak D is positive. We are thinking about changing to this process, as we now have to result many babies as "Rh Unknown" and give their mothers Rhogam.
Per our Anti-D's package insert: "Red blood cells coated with alloantibodies or autoantibodies of the same or similar specificity as the reagent (i.e. cells that are DAT positive) may give weak reactions. This is due to decreased availability of antigen sites because of antigen blocking or steric hinderance. In extreme cases false-negative results may occur."
I'm worried about the "extreme cases" where a false negative could occur, but I cannot see this being common. Also, would you think that if the cells were coated with that much antibody, that we would see any other odd reactivity in the ABO/Rh? What do other facilities do?
Thank you in advance,
Susan