1. There are test now to prove if someone has CFS.. One just got approved by FDA... look it up.
2. There have been reports from people who have CFS and took ampligen and loved it. It helped them out and when they went off everything went back to the way it was.
3. note, Ampligen is not a treatment and FDA knows that. Its a coping medication, like taking pain meds after surgery. it just makes you feel better. It is a immune booster... thats why it is good for many diseses cause it boost your IMMUNE SYSTEM
I think your point #2 says it all: some reported positive results. There are no drugs reported as having 100% results on everyone tested. Some have allergies and others have other issues. Some have no issues. Doctors are the ones responsible to do the screening and subsequent medication adjustments, not the FDA.
There is no diagnostic test for Chronic Fatigue Syndrome. Here is the latest info on diagnosis from The Chronic Fatigue and Immune Dysfunction Syndrome Association of America, the oldest and largest CFS organization in the U.S.