- Blood samples showed hormonal and immune differences in people with long Covid
- People with long Covid symptoms had cortisol deficiency and dysfunctional T cells
- READ MORE: The long covid has left me full of pain and exhausted
Blood tests from people who claim to have long Covid show that people who suffer from the condition have different biological differences from those who do not.
The report provides the first evidence showing that people who suffer from this difficult-to-define condition have notable differences in their biology compared to those who do not suffer from it.
The results of the study, the first of its kind, mark an important advance in the diagnosis and treatment of this perplexing disease with which approximately nine million Americans live.
Long Covid consists of a constellation of symptoms that persist after someone has recovered, including relentless fatigue and mental confusion. Doctors often dismiss patients because they think it’s all in their head or some other condition entirely.
Researchers at Yale University and Mount Sinai Hospital relied on artificial intelligence to analyze hundreds of blood samples from people with and without long Covid. The biological differences they identified suggest that the symptoms could be treated with experimental medicine.
Long Covid is estimated to affect between nine and 20 million Americans. It is difficult to diagnose since most clinical diagnostic tests, such as urinalysis and x-rays, are normal. But the latest findings suggest that blood tests could be useful in identifying possible treatments for symptoms.

Identifying specific biomarkers of long Covid is a major victory for patients who have been repeatedly dismissed by doctors who believe their symptoms are all in their heads.
Their findings could pave the way for simple blood tests to diagnose long Covid, which has historically been difficult because clinical tests and x-rays typically return normal results.
The study, led by Dr. David Putrino, a physical therapist and rehabilitation expert at Mount Sinai, included an analysis of more than 270 blood samples from people who had fully recovered from a confirmed case of Covid, those with active Covid symptoms prolonged for at least at least four months after a confirmed COVID-19 infection, and those without prior Covid infection.
Dr. Putrino said: “These findings are important: they can provide a basis for more sensitive testing for long COVID patients and personalized treatments for long COVID patients that, until now, have not had a proven scientific basis.”
The analysis included samples taken between January 2021 and June 2022. It was based on both blood tests and a comprehensive questionnaire for participants to detail their symptoms, quality of life, and medical history.
Some of the biomarkers the authors of the groundbreaking study identified included the abnormal activity of a certain type of immune cell called T cells.
Malfunction of these cells can cause to the chronic inflammation that is believed to be behind a host of long Covid symptoms ranging from fatigue and joint pain to cognitive problems.
Researchers also found that compared to those who had short-term Covid, people with symptoms had about half the amount of cortisol, the body’s main stress hormone.
An insufficient amount of this hormone, among other effects, causes fatigue, problems falling asleep at night and waking up in the morning.
Finally, the team identified that the common Epstein-Barr virus had lain dormant in Covid sufferers for a long time and then reactivated.
This virus causes mononucleosis, commonly known as mono, and is thought to contribute to many long Covid symptoms.
Dr. Akiko Iwasaki, a biologist at Yale School of Medicine and co-author of the study, said, “We are excited to see such clear differences in immune phenotypes in people with and without long COVID.”
“These markers need to be validated in larger studies, but are a first step in analyzing the pathogenesis of long COVID disease.”
The machine learning algorithm they used was able to distinguish people with long Covid from those without with 96 percent accuracy.
Dr. Putrino added: “This work is very exciting because it is one of the first to show us clear, measurable differences in the blood biomarkers of people with long COVID compared to people who have fully recovered from an acute infection and a group of people who have never been infected with SARS-CoV-2.
“These findings show us that people with long COVID live with a disease process that is observable through the blood testing protocols established in the study, but that also varies from patient to patient depending on their specific medical history.”