I don't know the definitive answer to your question, but this is my take on disease progression. When my rheumy says it has been observed to slow the progression of the disease, I think he means that it won't just get rid of the joint pain, it will lessen the inflammatory response so that numerous symptoms will decrease. There aren't hard and fast measures to determine disease progression. If your existing symptoms get worse and you get new ones, you can say your disease is progressing. If your symptoms quiet down and you're not getting new ones, it seems like your disease progression is slowing down. When I was first put on plaquenil, he didn't also give me other drugs right away because he thought that many of my symptoms might improve and he wanted to see if that was true before adding other drugs. (It was.) Later on, when I started getting skin rashes from the sun, he said that sun exposure would increase disease progression, meaning I could expect more joint pain, fatigue, etc. as well as the skin rash, from any sun exposure I got (I covered up quick). Does this make sense?