Using tests or assays to determine the worthiness for selection is important, certainly. Testing for VSH helps when selecting for mite resistant breeding stock.
However, keep in mind that the goal of breeding is to pull out of the random assortment of trait combinations that make the phenotype, the genetic potential for desired phenotypes.
If the goal in a breeding program is to have hardy healthy bees that one may manage "treatment free", testing for VSH is one of several selection criteria.
That's where the "AND" from my previous post comes in. Selection requires good test results AND bees that one feels are good. If one only selects for bees that have very high VSH expression
one will have that, but the bees might not be that nice/pleasant to work with.
Using VSH testing is a selection tool. If you combine VSH testing (use a few of the tests: the url for the tests have been posted to beesource many times) with other selection tests, you'll see some form of progress.
The reality of selection's practical application is that is works more effectively in decent sized populations. Selection pools that are larger, will have a higher probability of more desirable selection candidates.