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Scientists in Vancouver have developed a new screening tool that reveals the genetic signature of an individual's hepatitis C virus so that doctors can customize their treatment.

The tool, funded by Genome B.C. and devised by researchers at the B.C. Centre for Excellence in HIV/AIDS, could save money and lives, said Anita Howe, scientific lead for the hepatitis C program.

"I would be able to tell you whether you are infected with a [virus] with resistant mutations," she said. "By doing that, I would be able to know what type of drugs to prescribe to you to increase your success rate."

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Hepatitis C is a virus that targets the liver. Worldwide, 170 million people are infected with it, including 250,000 in Canada. Unlike hepatitis A and B, this virus doesn't have a vaccine.

There are drugs – called direct-acting antivirals – that are effective at clearing hepatitis C from the body, but they are incredibly expensive. One treatment round can cost between $45,000-$100,000 a patient. In British Columbia, public funding for those drugs is restricted to patients with certain hepatitis C genotypes and advanced liver scarring.

Most drug regimens have success rates greater than 95 per cent, as long as the virus hasn't developed any drug-resistant mutations. But hepatitis C is a rapidly mutating virus and sometimes those mutations confer resistance to certain drugs. Choosing a drug cocktail that will work on the virus is essential.

"If you are infected with an NS5A drug-resistant virus and I don't know and I use this powerful, expensive NS5A-inhibitor drug to treat you, it is going to waste that treatment," Dr. Howe said. NS5A drug resistance occurs naturally in 12 per cent 18 per cent of hepatitis C patients.

"If I had known that [your virus has] a resistant mutation to NS5A-inhibitor drugs, I would have prescribed you another type of drug," Dr. Howe said.

The new screening tool would let doctors do that.

Dr. Alnoor Ramji has already taken advantage of the new test for his hepatitis C patients.

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"In the majority [of patients], you're not going to find anything," he said. "Which is great. But in the few that [have resistance], you may be able to provide more effective therapy."

Dr. Mel Krajden, with the BC Centre for Disease Control, said the test is especially important for patients whose first round of treatment didn't work.

"This test should be used for patients with late-stage disease and people who have [previously] failed therapy," he said. "Because they're the most likely to develop antiviral resistance."

When a treatment course fails – meaning it fails to eradicate the virus from the body – it becomes more likely that the virus will develop drug-resistance, making it critical to find the correct treatments for patients in the second or third round of treatment.

"From a public-health perspective, curing [people with drug-resistant viruses] is going to be more challenging," Dr. Howe said. "They are going to transmit the resistant viruses. Just like multi-drug-resistant [bacteria], this is going to spread."

The majority of patients, however, will be cured with a course of antivirals, with no need for resistance testing.

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The B.C. Centre for Excellence in HIV/AIDS has been absorbing the cost of conducting the new test. The provincial government doesn't cover it, but Dr. Howe is hoping that will change soon.

Dr. Howe's work also includes looking at how virus genetics might differ in populations with a high risk of re-infection for hepatitis C, such as injecting drug users. She's also part of a global effort to establish a hepatitis C resistance database, to share virus genomic profiles from around the world.

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