First UK National Database Measures Levels of HIV Drug Resistance

The UK Health Protection Agency's Communicable Disease Report published the first data from the National HIV Resistance Database, which show that HIV drug resistance is increasing. "Drug treatments for HIV have proved to be very successful in keeping many of those infected in good health; however, in a small number of people the resistance to these drugs is steadily increasing," said Dr. Barry Evans of the HPA.

The National Resistance Database looks at levels of resistance in two groups: patients who are not responding to drug regimens or who responded well initially but have subsequently begun to fail on treatment, and treatment-naive patients who have become infected with drug-resistant HIV.

The percentage of treatment-naive patients infected with drug-resistant HIV rose from 10 percent in 1996 to 14 percent in 2001. The figures mean that a number of people are contracting the virus from patients who are, or were, receiving therapy.

Among patients for whom drug therapy is not working, the percentage with resistance to any one HIV drug has remained stable at 70-80 percent since 1996, Evans said. The greatest concern is the number resistant to all three classes of drugs. That percentage has increased from 1 percent in 1996 to 14 percent in 2001, reflecting the tendency of the virus to mutate and replicate despite treatment.

"It is important to bear in mind when looking at these figures, that we are not able to test for drug resistance in all patients with HIV. To be able to look at levels of resistance there must be above a certain amount of virus in a patient's blood, and if treatment is successful the amount of virus will be suppressed, meaning there will not be enough detectable," Evans said. "Drug resistance testing only tells us about the virus in patients in whom therapy is not working, or in whom therapy has not yet started and is not a reflection of all patients receiving treatment.

"There is still a need to continue to develop new classes of HIV drug treatments, in order to effectively treat people who are experiencing treatment failure," Evans explained. "New diagnoses of HIV infection in the UK continue to rise, and safer-sex messages targeted at people living with HIV are essential in order to prevent onward transmission of drug-resistant strains of the virus to newly infected individuals."

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