- Home>
- Specialty Care>
- HIV/AIDS>
- Top Story
Resistance Testing: A New Emphasis on Detecting Transmitted Resistance
All HIV-infected patients should undergo genotype testing prior to initiation of antiretroviral therapy.
The April 2006 update of the U.S. Department of Health and Human Services (DHHS) HIV treatment guidelines advocates resistance testing prior to initiation of antiretroviral therapy in all HIV-infected patients, whether they have longstanding (chronic) or recently acquired (including acute) infection. The guidelines also suggest pretreatment resistance testing for newly diagnosed patients not yet in need of therapy in order to guide antiretroviral treatment decisions in the future.
The need to assess treatment-naive patients for transmitted resistance was demonstrated in a large collaborative study referred to as CASCADE (Concerted Action on Seroconversion to AIDS and Death in Europe). This cohort included patients diagnosed with acute and recent HIV infection in Europe and Canada between 1987 and 2003. About 10% had evidence of intermediate- or high-level genotypic resistance, according to the Stanford algorithm. Rates of pretreatment resistance appeared to increase over time (ACC Jan 4 2006).
Further support for genotypic testing in treatment-naive patients was provided by two treatment studies published this year — the first from a cohort of acutely infected patients in New York whose treatment regimens were selected based on the results of resistance testing. Virologic responses were similar in patients who had transmitted resistance and those who did not (ACC Jun 14 2006). The second study described a cohort of 269 HIV-infected patients in Germany. Genotypic resistance testing was performed on all patients, and the results were provided to their physicians before therapy initiation. Virologic and immunologic responses were comparable between those with transmitted resistance (about 11% of the cohort) and those without (ACC Jun 14 2006).
HIV-infected pregnant women are a particularly important group in whom to consider the effect of transmitted resistance. Guidelines from both the DHHS and the U.S. Public Health Service emphasize the need for resistance testing among such women. The latter guidelines recommend the use of intravenous AZT during labor and delivery even in women with documented resistance to that drug. Neonates born to women with documented antiretroviral resistance should have a prophylactic regimen selected, preferably before delivery, with assistance from a pediatric specialist.
Many HIV clinicians have already adopted the recommendation to perform pretreatment genotypic resistance testing. Accumulated evidence indicates that detection of transmitted resistance allows selection of treatment regimens that yield success rates comparable to those achieved in patients without pretreatment resistance. With the excellent initial treatment regimens now available, this is good news indeed.
— Charles B. Hicks, MD
Published in AIDS Clinical Care December 29, 2006