The US Food and Drug Administration approved the first nucleic acid test for hepatitis B virus (HBV) that measures the amount of viral DNA (viral load) in a patient's blood. Assessing a patient's viral load provides health care professionals with a highly sensitive method for gauging the progress of antiviral therapy in patients with chronic HBV infections.

The COBAS TaqMan HBV Test extracts and then amplifies sections of viral DNA from human plasma or serum. The viral DNA sections are measured to establish a baseline level before beginning treatment, and then used again during treatment to assess an individual's response to therapy. (The baseline level of hepatitis B virus should decrease with successful treatment.) The test is used with other clinical findings, such as results from biochemical and serological testing.

The COBAS TaqMan HBV Test is manufactured by Roche Diagnostic Division, Basel, Switzerland, an US FDA press release said.

"Measuring a patient's HBV viral load is an important aspect of managing chronic hepatitis B infections," said Daniel G. Schultz, M.D., director of FDA's Center for Devices and Radiological Health. "The COBAS TaqMan test gives health care providers a new and sensitive tool for this process."

HBV is the most serious type of viral hepatitis, infecting about two billion people worldwide each year, according to the World Health Organization. A vaccine for HBV has been available in the United States since 1982. However, according to the Centers for Disease Control and Prevention, about 1.25 million people in the United States have chronic hepatitis B. Another 60,000 become infected each year and some 5,000 die from hepatitis B-related complications.

HBV is spread through sexual exposure, use of infected needles, and transmitted from infected mother to child during birth. Symptoms occur in about 70 per cent of patients, and include abdominal pain, jaundice, fatigue, loss of appetite, nausea, and vomiting.