This is a swtich that was made recently. I just work here if you know what I mean. Basically we are a smaller type BB and dont due a ton of DAT's but we do some especially cord bloods etc. Supposedly the difference is the C3d cards only contain half as much anit IgG because it also contains complement. WE did some comparisons etc. Ortho package insert says DAT testing only but we are investigating why it says this. Some ortho people said as long as some parellel testing is done and OK its acceptable.