I can't speak to whether it is routine to get a baseline off treatment, but I do think a DEXA scan is a good thing to have done at some point. My daughter has had two, one on treatment and one off. The one she had done during treatment was because a X-ray after a broken leg showed on its face that her bone density was strikingly reduced, and indeed, her DEXA scan showed that she was severely osteoporotic. She remains so off treatment (although we haven't had a scan done since last August, when she was 6 months off treatment). Long time steroid use greatly affects bone density. The scan will show whether your daughter should be taking supplements and how at risk she is for breaking bones, and it is a simple and fast procedure.