The immune systems of people with chronic fatigue syndrome differ from those of healthy people, and patients with recent diagnoses can be distinguished from those who have had the condition for longer, researchers reported on Friday.

The findings do not have immediate clinical applications for patients, experts said. But the biomarkers discovered by the scientists may eventually form the basis of the first diagnostic test for the illness.

“A biomarker has been the goal for much of the research for the last 15 years, so it’s really excellent that they have found something they consider significant,” said Dr. Birgitta Evengard, a professor of clinical microbiology at Umea University in Sweden and an expert on the illness.

The findings still need to be replicated in other labs with other groups of patients, cautioned Dr. Evengard, who was not involved in the research.