U.S. scientists say proteins in spinal fluid may help solve the confusion of symptoms between two similar diseases — chronic fatigue syndrome and Lyme disease.

Researchers say different sets of proteins discovered in the two groups of patients indicate these are distinct and distinguishable disorders and that both involve the central nervous system, ScienceNews.org reported Thursday.

Chronic fatigue is marked by prolonged and severe tiredness that isn’t resolved by rest and is often difficult to diagnose and treat. Women are most commonly affected.

Lyme disease results from a bacterial infection spread by deer ticks. It is treatable with antibiotics, but some patients continue to have longer-term symptoms, including fatigue.

Scientists have wondered whether such post-treatment Lyme problems are a form of chronic fatigue, but a connection has never been discovered.

In the study, researchers at the University of Medicine and Dentistry of New Jersey analyzed spinal-fluid samples from three groups — 11 healthy people, 43 diagnosed with chronic fatigue syndrome and 25 previously treated for Lyme disease but who were still experiencing cognitive problems and fatigue.

Of the more than 2,600 proteins found, most appeared in all three groups but 692 proteins turned up only in the Lyme patients and 738 others showed up only in the chronic-fatigue group.

Some of the condition-specific proteins may ultimately serve as biomarkers, researchers say, as identifying 20 or 30 proteins that show up consistently in a condition — but not in healthy people — could form the basis of a diagnostic test for the ailment.