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Top Ten Research Reports of 2003
8. Analysis From More Than 1,600 Newly Diagnosed Patients With HIV From 17 European Countries Shows That 10% of the Patients Carry Primary Drug Resistance: The CATCH Study

By David Alain Wohl, M.D.
University of North Carolina AIDS Research and Treatment Unit

February 2004

Wensing A. M. J., van de Vijver D. A. M. C., Asjo B. et al. Analysis From More Than 1,600 Newly Diagnosed Patients With HIV From 17 European Countries Shows That 10% of the Patients Carry Primary Drug Resistance: The CATCH Study. Presented at: 2nd IAS Conference on Pathogenesis and Treatment; July 13-16, 2003; Paris, France. Abstract LB1.


Viral resistance is not limited to those who have received HIV therapy. Data13 from U.S. investigators studying recently infected patients have found evidence of increasing antiretroviral-drug resistance, particularly to those drugs that have been available the longest. The CATCH Study was conducted in 17 countries in Europe and examined the incidence of genotypic resistance among persons newly diagnosed with HIV.

What Is New Here?

The study is a comprehensive examination of transmitted resistance that included people more than a year out from their acquisition of the virus. The investigators found that almost 10% of these treatment-naive participants had evidence of at least one major antiretroviral mutation. The prevalence of resistance to nucleosides was 6.9%, to non-nucleosides was 2.6%, to PIs was 2.2% and to more than two classes of agents was 1.7%.

Interestingly, the prevalence of primary resistance among patients with seroconversion in the previous year was 10.9% versus 7.5% in patients who had been infected for over a year (p=0.06). Further, the prevalence of resistance was significantly higher in patients with subtype B (11.3%) than in patients with non-B subtypes (3.3%), the latter likely representing people infected outside of Europe, in areas where access to antiretroviral therapy is limited.

The Bottom Line

These are dramatic results. That one in 10 people in Europe with newly diagnosed HIV infection harbors antiretroviral-resistant virus casts any argument against the use of resistance testing prior to therapy initiation in a new light. This study was unique in that it demonstrated that contrary to popular perception, the mutations were detectable in the majority of these treatment-naive patients who initially showed resistance even more than a year after infection.

The full implication of these resistance mutations for response to subsequent therapy is not yet known, but they are unlikely to be a good thing and, until evidence supports the contrary, they should be respected when initial regimens are being crafted. While resistance testing at initial evaluation is not always within the capacity or budget of many clinics, this study supports such testing when it is possible. In addition, efforts to reduce HIV transmission risk behavior among HIV-infected people must increase to limit the spread of the virus, resistant or otherwise.


  1. Little S. J., Holte S., Routy J.-P. et al. Antiretroviral-Drug Resistance Among Patients Recently Infected With HIV. New England Journal of Medicine. 2002 Aug 8; 347(6):385-394.

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