Patterns in the genetic code of hepatitis C may help predict which patients infected with the virus are likely to respond to treatment, researchers have found.

In Monday's online issue of the Journal of Clinical Investigation, John Tavis of the Saint Louis University school of medicine in Missouri and his colleagues said they used a "covariation analysis" to predict the outcome of therapy in people infected with hepatitis C.

"What we found will allow a doctor to predict whether or not a medication will work in a patient," Tavis said.

People with hepatitis C are typically given two powerful drugs, including a type of interferon, for 24 to 48 weeks. The therapy can cause patients to "feel like they have a very bad case of the flu for a year," Tavis said, and only works in half of all patients.

Interferon is part of the body's natural defense system against viruses, but the hepatitis C virus fights back against the effects of the drug.

In the study, the researchers mapped the virus's genetic code in 94 infected patients. The team found chunks of code that were always linked with failure of therapy, which the researchers say could help predict whether standard hepatitis C therapy will work in a patient.

Stick with therapy

"The side effects of the medicines to treat hepatitis C are terrible," Tavis said. "Why beat on a patient for a year if the treatment isn't going to work anyway?

"On the other hand, if we know the medicine is likely to work, we can coax patients to stick with the therapy. It would help doctors to positively support their patients through trying times."

A course of the treatment also costs up to $30,000 US, while a proposed test to determine whether a patient is likely be benefit from the therapy could be developed for about $100 US per sample, the researchers said.

"The ability to predict such failures prior to treatment could save a great deal of pain and expense for the patient with" hepatitis C virus, Thomas Oh and Charles Rice of Rockefeller University wrote in a journal commentary accompanying the study.

"Such analyses suggest markers predictive of response to therapy and may lead to new insights into the underlying biology of hepatitis C."

The results of the study may also help in identifying targets for new antiviral drugs, the study's authors said.

An estimated 250,000 people in Canada are infected with hepatitis C, according to Health Canada. The disease causes inflammation of the liver and, in some cases, severe damage or cancer in the organ. Some people may appear tired and jaundiced during the initial infection phase, but many show no symptoms.