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Nearly one in five patients with HIV infection continues to be treated by drugs to which their HIV has tested resistant

Testing for HIV resistance to antiretroviral therapy (genotype resistance testing) has become part of the standard of care for patients with HIV infection. Yet, 18 percent of patients, whose doctors found HIV resistance to the antiretroviral medication they were taking, continued to be treated with that medication. Continuing this medication was associated with significantly weakened reduction in the patient's HIV viral load. Thus, the progression of HIV disease was not being slowed as much, indicating reduced medication effectiveness.

The investigators looked at the medical records, including lab test results, of patients with HIV infection seen at 10 HIV specialty clinics in 7 U.S. cities since 1993. They analyzed the frequency with which patients were prescribed any non-nucleoside reverse transcriptase inhibitor after identification of the K103N mutation in reverse transcriptase and the frequency with which they were prescribed nelfinavir after identification of the D30N mutation in HIV protease. They also examined the short-term impact of this action on HIV viral load and CD4 T-cell count (indicators of disease progression).

Among the 441 patients demonstrating either mutation, 18 percent who were taking the resistant antiretroviral at the time of the test were continued on the medication for more than 6 months later. The doctors said that in one third of cases, the continued prescribing of the resistant medication was an erroneous oversight.

Patients who stopped the resistant antiretroviral within 6 months of the test fared better. They had greater decreases in viral load and a greater likelihood of achieving an undetectable viral load 9 months later. Patients who discontinued the medications also had an increase in CD4 T-cell count (indicating improved immune system functioning) compared with those who continued use, but the difference was not significant.

The study was supported in part by the Agency for Healthcare Research and Quality (HS11800).

More details are in "HIV genotypic resistance testing to optimize antiretroviral prescribing: Is there room for improvement?" by Jonathan Uy, M.D., John T. Brooks, M.D., Rose Baker, M.S., and others, in Antiviral Therapy 12, pp. 957-962, 2007.

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