QUOTE (Heath Robinson @ Dec 21 2009, 05:04 PM)

Bone density is measured in terms of the number of standard deviations above or below the mean for the ethnicity and gender of a particular person. Bone density is naturally variable and probably follows a normal distribution. In other words, you have a trade-off between false-positives and false-negatives. If you set the cutoff higher, then you will see fewer mistaken identifications of normal people as having dangerous combat augmentations, but you will also miss people who have had said augmentation whilst having a lower than normal bone density to begin with. Furthermore, there is little to say that BDA is, by necessity, a universal treatment. It is likely that one could tailor the profile of the augmentation to mimic the kind of natural response to trauma.
This deviation from the mean that you describe is a standard deviation from normal. In order to give the benefits listed in SR literature, bone density augmentation would have to be a density far above normal (an outlier). While one can argue that a higher bone density achieves a higher augmented Body attribute and thus can be analogous to people with higher Body attributes in Shadowrun (in simple terms, a person with a 3 Body with 3 points of BDA similar to a bone density of a person with a 6 Body, for example), being able
to punch as hard as someone whose bones are laced with plastic or titanium is NOT normal, and the density would be an outlier above normal to achieve that (to the point where the bones would be less plastic and more brittle*, unless reinforced... and this reinforcement would be seen on an X-ray).
Most radiologists are fairly good at identifying changes in the bone specifically, whether from artificial or natural causes. According to most journal articles, they are especially good at detecting small changes (within 10% of mean) and large changes (greater than 60% of mean), and are better than bone density scans at determining artificial anomalies. The common radiograph is a remarkably good tool for this, and although it depends on the skill of the viewer, a radiologist sees hundreds of X-rays (if not more) a week.
I can see your point, and in your game, you may wish to enforce that point. We can argue over the numbers until we are blue in the face (right now, we are being very civil and I don't feel that we are arguing), and it wouldn't really answer anything (being a fictional game and all, and a poorly thought-out piece of bioware, biologically speaking). I've had a lot of personal experience with radiologists, so I know how good they can be at pointing out bone disease on seemingly innocuous X-rays. I don't see that the ability to punch people with a force harder than a baseball bat as being within the standards of normal for bone structure.
Still, if the standard for determining bone density remains the typical bone density scan, there are ways that you can trick and fool those scans biologically (inserting certain inert compounds into the bone to increase structural integrity while fooling the scan, for example), all of which could be the realm of deltaware or other high grade bioware.
* While it may seem counter-intuitive that increased bone density would cause more fractures without reinforcement, this is actually one of the concerns with the current regimen of bisphosphonate drugs on the market today.