(NBC, KYMA/KECY) - There may be some clarity coming for those who suffer or have suffered from 'long COVID.'
Scientists have found clear differences in the blood of people with long COVID, a key first step in the development of a test to diagnose the illness.
The findings also offer clues into what could be causing the elusive condition that left millions with ongoing fatigue, trouble with memory, and other debilitating symptoms.
The activity of T-cells and B-cells, which fight off germs, was "irregular" in long COVID patients.
Long COVID patients tended to have significantly lower levels of a hormone called cortisol.
A major function of the hormone is to make people feel alert and awake. Low cortisol could help explain why many people with long COVID experience profound fatigue.
Scientists plan to dig deeper into the role cortisol may play in long COVID in future studies.