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HIV resistance testing at diagnosis improves survival, cost-effective
By Megan Rauscher
NEW YORK (Reuters Health) - The results of a new study demonstrate that HIV drug-resistance testing at the time of diagnosis -- before the start of antiretroviral therapy -- is a cost-effective strategy that can lead to the selection of a more effective initial antiretroviral regimen and likely improved survival.
Reporting their findings in the November 1st issue of Clinical Infectious Disease, now available online, study investigators say resistance testing at the time of diagnosis "should be the standard of care" for all patients newly diagnosed with HIV infection.
To determine the clinical impact and cost-effectiveness of front-line HIV resistance testing, Dr. Paul E. Sax and colleagues used a computer simulation model of HIV disease that projects life expectancy, costs, and cost-effectiveness.
Using a baseline drug resistance prevalence of 8.3%, resistance testing of newly diagnosed, antiretroviral-na´ve HIV-infected patients was associated with "better survival at a very reasonable cost," study chief Dr. Sax, clinical director of the HIV Program at Brigham and Women's Hospital, Boston said in a telephone interview with Reuters Health.
The cost-effectiveness ratio of front-line resistance testing was $23,900 per quality-adjusted life-year (QALY) gained -- well below the commonly accepted threshold for cost-effectiveness of $50,000 per QALY.
The $23,900 per QALY gained, the authors point out, "is in the range of other commonly accepted HIV interventions, including resistance testing after treatment failure ($20,200 per QALY gained), combination antiretroviral therapy ($25,900 QALY gained), and prophylaxis for Mycobacterium avium complex infection ($63,100 per QALY gained)."
"Even if you lower the resistance rate down to just above 1%, resistance testing for newly diagnosed patients is still pretty cost effective," Dr. Sax said.
Currently, "around 8% to 10% of patients diagnosed with HIV in the US now have some form of resistance to antiviral drugs right from the get-go," he added.
He also noted that while "a lot of clinicians are doing resistance testing already," resistance testing for all newly diagnosed patients is not "emphatically stated" in current guidelines, unless HIV infection was acquired recently or the prevalence of baseline resistance exceeds 5%.
The hesitation to employ resistance testing for all HIV-infected patients stems from multiple factors, most notably the cost of the test, which stands at about $400 per test, and the absence of controlled data showing that such as strategy improves outcomes.
"On the basis of the available evidence, and considering both clinical benefits and costs," Dr. Sax and colleagues conclude, "genotype resistance testing should be performed for all patients with newly diagnosed HIV infection in the United States, with the results used to guide the choice of antiretroviral regimen when treatment is indicated."
The authors of a related editorial agree. For now, however, the work of Sax et al. leaves clinicians with a perplexing problem, Dr. Frederick M. Hecht and Robert M. Grant from San Francisco General Hospital in California point out.
Existing recommendations and current reimbursement in many programs restrict resistance testing for drug-na´ve persons to those who are recently infected, they explain. "In most patients, however, the duration of infection cannot be discerned from the history or clinically available laboratory tests."
Moreover, current recommendations to perform resistance testing when the prevalence of drug-na´ve patients is believed to be 5% or greater assumes that this information is available to clinicians, which in most communities is not the case.
The recommendation for genotypic resistance testing for all drug-na´ve persons with HIV is more easily implemented, and the article by Sax et al., shows that it is also cost-effective, Drs. Hecht and Grant conclude.
The issue of HIV drug-resistance testing for all newly diagnosed treatment-na´ve patients is currently being discussed by the International AIDS Society-USA panel.
Clin Infect Dis 2005;41:1316-1325.
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