Mehmet Oz, M.D., is host of “The Dr. Oz Show,” and Mike Roizen, M.D., is Chief Wellness Officer and Chair of Wellness Institute at Cleveland Clinic. Email questions to youdocsdaily@sharecare.com.

QUESTION: My sister may have chronic fatigue syndrome, if that’s a real thing. She’s been complaining that she’s always tired, nervous and has trouble thinking clearly. She’s only 35.

Is there any way to find out what’s really going on?

— Rachel M., Buffalo, N.Y.

ANSWER: Myalgic encephalomyelitis/chronic fatigue syndrome is a very real condition. Researchers at Columbia University in New York City have put together a test that delivers a diagnosis that’s 84 percent accurate.

Not that many years ago (actually, it still happens) patients who complained about extreme fatigue, anxiety and forgetfulness would get a pat on the head from their doctors, and the admonition to calm down and get some rest.

We now know that myalgic encephalomyelitis/chronic fatigue syndrome is a disabling and complex illness. The Centers for Disease Control and Prevention estimates it affects between 836,000 and 2.5 million Americans.

We don’t know what causes it, but one theory is that it’s caused by a change in the immune system’s response to infection or stress. The affliction usually affects folks age 40 to 60, most often women and Caucasians.

As for treatment, well, that’s another part of the puzzle. But accurate diagnosis is the first step.

The researchers at Columbia compared and identified biomarkers or metabolites in blood and stool samples in folks with myalgic encephalomyelitis/chronic fatigue syndrome and those without the condition. Between 35 and 90 percent of those with a diagnosis had irritable bowel syndrome. In the general population, the number is 10 to 20 percent.

Previously, the only way to identify those with this syndrome was to conduct an in-depth evaluation of the patient, considering past symptoms and medical history. Now, thanks to this new research, we will be able to identify the disease (most of the time) with a blood test.

So, suggest that your sister find a specialist in her area and establish a diagnosis for her symptoms. If she is diagnosed, treatment focuses on managing symptoms such as fatigue that doesn’t get better with rest, difficulty concentrating, pain and dizziness.