I work at a small hospital that has been using tube LISS for antibody screens. We rarely get positive screens and when we do, we send them out. As I plan to change to PeG or Gel how large of a study should I do before I make that change? From my statistics class I recall that 30 is a good number. Any suggestions?

Thanks Ruth

Thirty is a good number. Even though you are a smaller hospital it shouldn't take forever to get 30 absc. Were you planning on doing a certain number of positives and negatives or just the first 30 that walk in the door?

You should be able to get positive samples from someone else--I was thinking ARC recently volunteered this. Maybe they could even send some weaker ones for your comparison. I'd get D, E, K at least, maybe Kidd (even though you will only be validating screens) to be sure there is no difference between methods with different specificities.. You could always ask for a warm auto just to be sure you will be able to detect it adequately.

ARC probably also has neg samples. Maybe you could just get a batch and do it all at once.

When I did our crossover study, I was able to obtain positves from other hospitals in our region. They were glad to help me out.