I understand the purpose of a baseline. However in the case of some tests they are not good indicators because they more or less measure, as an example, what is in your bloodstream and not in your cells, OR the conditions need to be EXACTLY timed between the first baseline and subsequent tests, OR the equipment is not calibrated EXACTLY to the equipment you had the original test on OR the radiologist doing the "read" interprets differently than the first OR you ate something the night before one of the tests that shows up in one test and not the other. There are many reasons that tests don't work as good baselines OR a stable predictive measurement between a first and subsequent test. Sometimes, it takes repeats over time and controlling conditions to really come up with accurate accounting. There is a lot of faulty and unreliable tests so the doctors don't want patients to worry. The proof will be tested over time with a trend line. They can't measure every available bone in my body to get an accurate assessment. When people get compression fractures, THAT is how they are diagnosed. Not before a fracture.