I found this article about a possible test to find out if anti-TNF meds will work for people with RA (still in the study phase, but interesting).

http://www.medicalnewstoday.com/articles/177627.php

Basically, they may be able to take from the level of certain kinds of interferon in your body, whether you're likely to respond to meds like Remicade, Enbrel & Humira that inhibit TNF in your body.  If you don't have a high level of these kinds of interferon, you might need something like Rituxan instead.  (I guess this assumes one has already tried the less expensive drugs first?)

    Of course, that doesn't take care of the problem of "which anti-TNF drug?" might be the best for you - some people have more side effects with one drug than another, and right now, it's just trial and error.