Yesterday we had a post-partum specimen for a Rhogam workup including FMH screening. The screen was 2+ macroscopically. We had no previous history and had not done any weak D testing on her, which is our protocol. Her prenatal specimen was sent to a commerical lab that most likely does not do weak D testing on D Negatives. We performed weak D testing and it was positive which invalidated the FMH screen. A Kleihaur Betke stain was negative. The physician wanted to give the Rhogam to her, which we did. When you have no history, as in this case, a situation like this in the hands of an inexperienced tech could have been misinterpreted as a VERY positive FMH screen which would have been resolved by the negative KB Stain, but would have left the tech who didn't consider that the patient might be a weak D confused.