Ask Dr. Jeff
Question: I am about to start taking antiretroviral medications for HIV, and I'm wondering if I should get a resistance test before beginning treatment.
Answer: It is becoming increasingly common for healthcare providers and people living with HIV to use resistance testing to predict the susceptibility of a person's HIV virus to specific anti-HIV drugs. The Public Health Service (PHS) Guidelines do not generally recommend that people beginning therapy for the first time, after being HIV-positive for an extended period of time, obtain a resistance test.
There are two reasons why resistance testing before initiating antiretroviral therapy in chronic HIV infection is not recommended. The first reason is that over time, most of the measurable virus in the blood becomes wild type, or non-drug-resistant HIV, even if someone was originally infected with a resistant strain. Second, most people infected more than a year or two ago are very unlikely to have been infected with drug-resistant HIV.
The guidelines do say that resistance testing should be considered prior to beginning therapy in primary (acute, or recently acquired) HIV infection. This consideration is based on recent data suggesting an increased incidence of transmission of drug-resistant HIV. At this September's 40th ICAAC meeting, reviewed extensively in this issue of the STEP Perspective (click here), studies were presented on transmission of drug-resistant virus. One study, presented by Dr. Beleaguer from Boston, was called "Prevalence of HIV Genotypic Resistance in Antiretroviral-Naive Patients Entering Care in Boston." The study included 45 adults. Major drug-resistance mutations were identified in 7 cases (16%): 5 for nucleoside reverse transcriptase inhibitors (NRTIs); 1 for non-nucleoside reverse transcriptase inhibitors (NNRTIs); and 1 for PIs). These types of data seem to support a more widespread use of resistance testing in primary HIV infection, if one decides to begin early anti-HIV therapy.
The current Public Health Service (PHS) Guidelines definitely recommend resistance testing only for people changing from a regimen that is not working, to assist in finding drugs for a new combination. It is becoming clear that the subgroup that appears to benefit the most from resistance testing is not those whose first regimen is no longer working (they still have a lot of choices), nor those who have been treated with almost every drug available (they probably have a lot of resistance), but those in the middle, who appear to have some treatment options available. For people in that middle group, resistance testing appears to allow selection of the most active drugs without using a combination of 7-9 highly active anti-retroviral drugs, "mega HAART."
This article was provided by Seattle Treatment Education Project. It is a part of the publication STEP Perspective.