Researchers in Israel have found markers in blood of people with multiple sclerosis (MS) that show up at least nine years before MS symptoms appear.
Basically, the researchers analyzed blood that had been taken from 19-year-old recruits into the Israeli army (as I understand it, they found 9 people who developed MS and went back and pulled their blood that had been taken nine years ago, when they were "healthy" and symptom-free). They compared this blood to 11 people who were matched to them on factors like age and gender, as well as to 31 people who were newly-diagnosed with MS.
The blood from the people with MS (both the 9-year-old blood and the newly-taken blood from the 31 people) had many genetic markers in common, which were absent from the blood of the 11 people without MS. These genetic markers indicate that certain immune cells, when "turned on," do not function normally. Researchers say that this indicates that the autoimmune process probably begins long before MS symptoms appear.
While the articles in the popular press, such as the Telegraph and The Jerusalem Post mention screening for MS, I think that probably won't happen, as: 1) there would be a very low return of positives, and 2) there is really nothing to be done for people who screen positive at this point. Many more samples need to be analyzed to know if everyone with these gene patterns will develop MS, or if these markers are "necessary, but not sufficient," meaning that other things (like a viral infection, for instance) had to occur to kick off the MS process.
Where I think a very exciting application may be is to test people who are displaying some sort of funky symptom, but where MRIs are inconclusive. I guess I am biased towards this because I was told that I probably had MS for 15 to 20 years before my diagnosis. In that time, I had seen at least 8 doctors for various symptoms. As I have relapsing-remitting MS, the weird sensations or problems would go away and the docs (and me) would forget about the whole thing. By the time most of us get to a doc for a formal diagnosis, we usually have experienced lots of different symptoms that just don't get identified as neurological in nature (like the MS hug, restless leg syndrome or headaches), rather than being truly "symptom-free."
Of course, there are also all sorts of amazing scientific discoveries that could happen that may eventually lead to different kinds of treatment or even prevention. This might also give clues as to the differences between the different types of MS.
If you want to read the scientific abstract to see exactly what is happening with the genetics of the immune system, here you go:
Achiron A, et al. Microarray analysis identifies altered regulation of nuclear receptor family members in the pre-disease state of multiple sclerosis. Neurobiol Dis. 2010 May;38(2):201-9. Epub 2010 Jan 14.