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The U.S. Food and Drug Administration has issued a warning to U.S. clinics performing studies on angioplasty as a treatment for multiple sclerosis, saying any studies on the procedure need FDA approval.

The FDA says it must give its stamp of approval to any studies analyzing the effects of the liberation treatment, which is a controversial area of research into the link between MS symptoms and blocked or narrowed veins.

The FDA's warning does not affect Saskatchewan MS patients travelling to participate in the clinical trial at the Albany Medical Center, a spokesperson for the government of Saskatchewan told CTV. The FDA gave final approval to the research protocol on May 4.

"Currently approximately 60 Saskatchewan MS patients have been screened. 45 of these patients are considered suitable candidates for Albany and will have a medical assessment by a neurologist in May. The first Saskatchewan patients will start traveling to Albany in June," the spokesperson said.

Saskatchewan is providing $2.2 million in funding to have 86 Saskatchewan MS patients included in the two-year clinical trial at Albany Medical Center in Albany, New York, headed up by Dr. Gary Siskin.

In the FDA's warning on Thursday, the agency said it has received reports of two adverse event reports from the procedure offered at a number of U.S clinics: one death and one stroke.

There have also been reports of detachment and migration of the stents that are sometimes used to open the veins; damage to the treated vein; blood clots; cranial nerve damage; and abdominal bleeding associated with the procedure.

"Because there is no reliable evidence from controlled clinical trials that this procedure is effective in treating MS, FDA encourages rigorously-conducted, properly-targeted research to evaluate the relationship between CCSVI and MS," Dr. William Maisel, the chief scientist and deputy director for science in the FDA's Center for Devices and Radiological Health.

The agency notes that balloon angioplasty devices and stents have not been approved by the FDA for use in treating CCSVI, the narrowed neck and chest veins that liberation treatment proponents say is linked to MS.

The agency says if doctors and researchers want to do clinical trials on CCSVI, they must comply with FDA regulations on investigational devices.

"Any procedures conducted are considered significant risk clinical studies and require FDA approval, called an investigational device exemption," the agency says.

FDA spokesperson Michelle Bolek explained that clinical studies that might pose a risk to patients always require approval from the agency.

"Clinical studies of significant risk medical devices, such as in the case of balloon angioplasty devices and stents to treat CCSVI, require approval through an IRB and the FDA's Investigational Device Exemption (IDE) program," she said.

"The IDE regulations help ensure the rights, safety and welfare of patients are protected during these studies and that the risks are as low as possible and are balanced by any potential benefits."

Earlier this year, the FDA sent a warning letter to Dr. Manish Mehta, a vascular surgeon in Albany, N.Y., after learning his clinic was offering a clinical trial of balloon angioplasty without FDA approval. That study did receive Institutional Board Review by other agencies.

Bolek said that if a clinic is simply offering the balloon angioplasty for CCSVI considered an "off label" use, they can continue to do so, providing they are not part of a prospective trial.

"Physicians who are treating CCSVI as part of the practice of medicine are not subject to Investigational Device Exemption regulations," she wrote in an email to CTV.

The therapy in question was devised by Italian physician Dr. Paolo Zamboni, who believes symptoms of MS may be caused or worsened by vein blockages that prevent blood from being drained from the brain. He calls the condition CCSVI, chronic cerebrospinal venous insufficiency.

The FDA says studies exploring a link between MS and CCSVI are inconclusive, and the criteria used to diagnose CCSVI have not been adequately established. Several studies are underway, including work at UBC, and another study in Albany New York, partially funded by the Province of Saskatchewan.

Scores of Canadians have travelled to the U.S and overseas to get the treatment; at least two Canadians are known to have died after undergoing the therapy.

Dr. William Maisel, the chief scientist and deputy director for science in the FDA's Center for Devices and Radiological Health, says patients considering the treatment should discuss the pros and cons with a neurologist or other doctor familiar with MS and CCSVI.

The liberation treatment was devised by Italian physician Paolo Zamboni, who believes symptoms of MS may be caused or exacerbated by vein blockages in the neck and chest that prevent blood from being drained from the brain. He calls the condition chronic cerebrospinal venous insufficiency or CCSVI.

The FDA says studies exploring a link between MS and CCSVI are inconclusive, and the criteria used to diagnose CCSVI have not been adequately established.

Several approved studies are underway, including work at UBC, and the one at Albany, partially funded by the province of Saskatchewan.