Test detects traces of resistant HIV

RALEIGH, N.C. — RALEIGH, N.C. -- A new test that detects whether patients with HIV/AIDS are infected with small amounts of drug-resistant forms of the virus has been developed by researchers at Duke University Medical Center.

The discovery, published online yesterday in the journal Nature Methods, could help doctors more accurately predict which medicines will work for patients and which drugs will ultimately fail. Current tests only pick up drug-resistant strains if they represent a significant portion of the virus circulating in a person's bloodstream.


Detecting resistance quicker would make it possible to keep patients healthy longer, reduce treatment costs and help cut an infected person's risk of spreading HIV. When drug treatment fails, the virus proliferates in the blood, causing an infected person to become more contagious.

"This can be huge," Dr. Feng Gao, a Duke researcher and co-author of the journal article, said of the new genetic test. Gao's lab at Duke perfected the testing process and conducted the experiments to prove its accuracy and sensitivity.


The test has been used for research purposes only, but Duke is seeking patents that would enable it to develop a diagnostic screening for commercial use. Duke still must show that the process helps improve treatment results.

"A lot of questions are still unanswered, but it's an important step forward," said Dr. Peter Leone of the University of North Carolina School of Medicine and medical director of the state's HIV prevention branch. If the test pans out, Leone said, it would "improve the odds that the first course of treatment is going to be successful."

Unchecked by drugs, the human immunodeficiency virus reproduces in an infected person's body at a dizzying rate. A single virus can make billions of copies of itself each day. The virus is not meticulous about making accurate copies, so tiny errors -- mutations -- occur as HIV replicates.

When a patient takes antiretroviral drugs, the medicines kill off the most prevalent strains of virus, enabling the mutations to survive and proliferate. Some of those mutations help HIV resist drugs.

Duke's new test comes amid rising evidence that HIV drug- resistance is a problem, even among patients who have never been treated with antiretroviral drugs.

Studies have found that 15 percent or more of patients newly diagnosed with HIV harbor drug-resistant strains of the virus.

Such findings helped prompt the federal government, which publishes national guidelines setting standards of care for patients with HIV, to begin recommending routine drug-resistance testing for newly diagnosed patients. The change, which took effect last year, means that most public and private insurance companies now cover resistance testing, which costs several hundred dollars per test -- $1,000 or more per test for certain types.

Even the less sensitive tests available now are helpful in avoiding treatment pitfalls, said Dr. Charles Hicks, an infectious disease specialist at Duke who treats patients with HIV/AIDS and is co-author of the journal article. A common mutant strain picked up by such tests resists one of the first-line treatments for HIV, he said. If patients test positive for that type of drug-resistant strain, doctors know to prescribe other medicines.


"It makes you choose a totally different treatment path," Hicks said.

Duke's test represents an improvement on existing lab tests because it is more sensitive, detecting resistant strains that make up less than 1 percent of the virus circulating in the patient's blood. Existing tests pick up drug-resistant HIV strains only if they make up 20 percent or more of the total virus in the patient's system.

"Even if you don't see resistance, you can't be sure that it's not really there," Hicks said. "That's a huge problem."