Scientific and Medical Evidence - Listing of Research conducted worldwide section :
The presence of crimson crescents in the mouth .
Scientific Findings in Primer for International Consensus Criteria (2012)

Get your doctor to look for crimson crescents in the the mouth and throat. This is an indicator of  HHV-6 infection and other viral infections. Dr. Burke A. Cunha, Chief of the Infectious Disease Division of Winthrop-University Hospital in Mineola, New York, has discovered arch-shaped, bright red, membrane tissue in the back of CFS patients' mouths. Located on both inner sides of the mouth next to the back molars, these "crimson crescents," as Dr. Cunha calls them, intensify in color as the patient's condition worsens, and fade as the patient improves.
Dr. Cunha states that the crescents appear in 80 percent of CFS patients but show up in less than 5 percent of non-CFS patients with sore throats, and not at all in patients with mononucleosis or strep throat. He states, "If your patient has crimson crescents, you now can say his condition is probably chronic fatigue syndrome."