An X-Ray will confirm that your bone is broken or confirm that it really is just a sprain, in the current moment. You are already in pain and need treatment right now. X-ray will help determine the method of that treatment.
A DNA test has the power to inform you of an illness you may have in the future, such as Huntington's disease, thus it is informing you of the potential of a future illness. Until that illness begins its course, you will be awaiting that illness. A DNA test will tell you that you may have some disease in the future, whereas an x-ray only informs you of the present moment. There is definitely a qualitative difference in those two examinations. Therefore it wouldn't be equivalent to opting-out of an x-ray. (For a more dystopic treatment, see the book "Next" by Michael Crichton; a wife divorces her husband and sues him because there is a DNA test showing he gave their children the predisposition for Huntington's disease [even though the children are very young and not yet affected by the disease])