Note that of all the different tests discussed, that many can not detect wear metals above 5-7 microns. Only test I saw in that paper was Ferrometry (Section 3.2.12) which said it can detect all ferrous wear particles above 0.1 micron. I believe a Blackstone type of UOA uses Plasma Emission Spectrometry (ICP - Inductively Coupled Plasma), and therefore is pretty insensitive in cases where lots of abnormal wear could be going on. You would probably see a slight uptick in the detected wear metals (ie, ppm per 1000 mile), but it wouldn't be a big red flag because that type of UOA is just too insensitive by only seeing a small sliver of particle sizes. This has been discussed in quite a few threads here, and a few examples given. A slight uptick was seen over the history of UOAs, and then further investigation (visual inspection of filter, visual inspection of machinery) showed a major mechanical failure was occurring.