New Blood Test Detects Chronic Fatigue Syndrome — Could It Be Adapted for Long COVID?

Researchers report promising blood-based signature for CFS; adaptation for long COVID remains possible but unproven

Scientists have developed a blood test that distinguished people with severe Chronic Fatigue Syndrome (CFS) from healthy volunteers in a small study. The research, published in the Journal of Translational Medicine, identified distinct genetic and other biological markers that the authors say could form a measurable “signature” of CFS.

Study design and key findings

The study compared blood samples from 47 people with severe CFS to 61 healthy controls. Researchers reported that their test correctly identified people with CFS with about 92% sensitivity and correctly identified people without CFS with about 98% specificity. The analysis detected hundreds of biological differences between the two groups and a consistent pattern in those with CFS.

Why this could matter for long COVID

Lead author Dmitry Pshezhetskiy, PhD, a research fellow at the University of East Anglia, notes that CFS and long COVID share some biological features. Because both conditions may produce overlapping changes in DNA expression and other blood markers, a similar testing approach could potentially be adapted to help detect long COVID. However, the authors emphasize that adaptation would require additional validation and retuning in larger, independent cohorts.

Limitations and cautions

• The study sample was small and focused on people with severe CFS, so results may not generalize to milder cases or broader populations.
• The research was funded by a biotech company involved in developing the test, which raises the importance of independent replication.
• More extensive, independent studies are needed to confirm the findings and to determine whether a CFS-derived test can reliably detect long COVID.

Clinical perspective: James C. Jackson, PsyD, research professor of Medicine at Vanderbilt Medical Center, says an objective test for long COVID would be extremely helpful because current diagnosis often relies on excluding other causes — a process that can be slow and frustrating for patients.

What this means for patients

The blood test is still in development and not yet available clinically. If you have persistent fatigue, shortness of breath, brain fog or other symptoms that might indicate CFS or long COVID, talk with your doctor. If your concerns are dismissed, consider seeking a second opinion or referral to a specialist.

Context: The Centers for Disease Control and Prevention (CDC) estimates that CFS affects roughly 3.3 million people in the U.S. and that about 17 million people reported long COVID in March 2024. While these conditions remain difficult to diagnose, research like this points to a possible path toward objective testing — but it is not yet definitive.