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Researchers say most of the people misdiagnosed with multiple sclerosis had been treated for the disease for years. Getty Images

The misdiagnosis of multiple sclerosis (MS) is a problem with significant consequences for patients as well as the healthcare system.

There are nearly 1 million people in the United States living with the disease.

And researchers now say nearly 20 percent of them are misdiagnosed. Most of them had another condition but had been treated for MS for years.

“The diagnosis of MS is tricky. Both the symptoms and MRI testing results can look like other conditions, such as stroke, migraines, and vitamin B-12 deficiency,” Dr. Marwa Kaisey, a specialist in neurology at Cedars-Sinai Medical Center in Los Angeles and a co-lead investigator of the study, said in a statement to Healthline. “You have to rule out any other diagnoses, and it’s not a perfect science.”

The study looked at 241 patients across three campuses and will be published in the May issue of the peer-reviewed journal Multiple Sclerosis and Related Disorders.

Kaisey, along with co-lead investigator Dr. Nancy Sicotte, interim chair of neurology and director of the Cedars-Sinai Multiple Sclerosis and Neuroimmunology Center, and researchers from the University of California, Los Angeles (UCLA) and the University of Vermont, analyzed patients who had been diagnosed by other physicians and then referred to the Cedars-Sinai or UCLA multiple sclerosis clinics over the course of a year.

Investigators wanted to see how many patients were misdiagnosed with MS and identify common characteristics among those who had been misdiagnosed.

The research found that almost 1 in 5 patients who came to the medical centers with a previous diagnosis of MS didn’t fulfill the criteria for that diagnosis.

On average, researchers said, these people spent four years getting treatment for MS before receiving a correct diagnosis.

“When we see a patient like that, even though they come to us with an established diagnosis, we just start from the beginning,” Sicotte said.

The most common correct diagnosis was migraine (16 percent), followed by radiologically isolated syndrome, in which patients don’t experience symptoms of MS even though their MRI results may look like the disease.

Among those misdiagnosed, 72 percent had been prescribed MS treatments. Forty-eight percent of these patients received therapies that carry a known risk of developing progressive multifocal leukoencephalopathy (PML), a serious disease in the white matter of the brain.

“I’ve seen patients suffering side effects from the medication they were taking for a disease they didn’t have,” Kaisey said. “Meanwhile, they weren’t getting treatment for what they did have. The cost to the patient is huge — medically, psychologically, financially.”

Researchers estimated that the unnecessary treatments identified in this study alone cost almost $10 million.

The researchers said they hope the results of this study will help improve diagnostic procedures and prevent future MS misdiagnoses.

“The first step, which is what we’ve done here, is to identify the problem, so now we’re working on potential solutions,” Kaisey said.

“This news is alarming and concerning,” Bruce Bebo, PhD, executive vice president of research at the National Multiple Sclerosis Society (NMSS), told Healthline. “The study was done before the most recent update to the McDonald’s diagnostic criteria was published in December 2017.”

“We’ve made great strides over the last few decades, especially with the MRI, but this study shows we need more help with diagnosis with MS,” he said. “We are looking forward to learning if this rate is reduced in the long run as a result of the criteria diagnostic.”

Because the diagnosis of MS and new treatment algorithms are complicated, it’s often helpful to have a consultation with an MS specialist to review diagnosis and treatment.

For example, migraine, the most common correct diagnosis, may present an imaging signal on an MRI that could prompt the confusion.

The NMSS lists diseases to rule out during the diagnosis process.

In 2016 researchers estimated total all-cause healthcare costs, including direct and indirect costs, ranged from $8,528 to $54,244 per patient per year. Data sources ranged from 1999 to 2008 and don’t include some of the newer, more costly therapies.

MS therapies have significantly increased in cost. Two new drugs approved by the Food and Drug Administration in March were priced at $88,500 and $99,500.

Healthline spoke with Laura Kolaczkowski, a patient advocate, writer, and patient co-investigator for iConquerMS.

“There is a danger in pushing for an MS diagnosis when there isn’t clear and convincing evidence, as they found through this study,” she said. “People really must be seen by a neurologist who specializes in MS and not just general neurology and have a thorough neurological exam.

“When you are diagnosed with MS it changes so many things in our lives, and to undo that mark on the medical record is complex, if not impossible. Even if you have to travel great distances to have a diagnosis confirmed at an MS center, it can be worth the time and effort,” Kolaczkowski said.

There are approximately 70 MS clinics in the United States. These clinics, as well as a list of neurologists who specialize in MS, can be located at the Consortium of MS Centers.

The NMSS provides a resource on its website to help find an MS specialist. The Mayo Clinic offers a variety of MS-specific campuses in Arizona, Florida, and Minnesota.

“But not everyone has access to an MS specialist. The society is aware of the issues of access to quality MS care and is making significant investments in this area,” Bebo noted.

“It is a complicated problem which needs to be addressed,” he said. “It emphasizes the importance of doctors using the new diagnosis criteria.”

Editor’s note: Caroline Craven is a patient expert living with MS. Her award-winning blog is, and she can be found on Twitter.