I thought I saw a post stating that Interferons only work on 1 in 5 people and that there is a blood to determine this. My neuro has not offered this test. I want to talk to him about it, but need more information so that I can speak intelligently about it. He generally shakes his head at me when I ask about things I learn on line, but usually humors me. Avonex makes me feel like poop for at least 36 hours every week. If it's working, I'm willing to deal with it, but if it's not I'm going to end it! Thanks for any information you may have.