The baseline population describes the volunteers when they started the study and may be expressed as range of CD4+ counts or viral loads, previously treated or untreated with antivirals or as symptomatic or asymptomatic.

The size and length of the study refers to the number of volunteers (or subjects) participating and the length of time they were studied or treated with anti-HIV medications. The results of long studies and large studies of 250 volunteers or more are considered more convincing than small or short studies.

Compliance may refer to the degree to which volunteers were able to take the treatments in the doses and at the times required. High rates of non-compliance or drop out rates may raise questions about the results of the study. Non-compliance was implicated in nearly all studies where HIV levels returned towards baseline. Also, compliance with potent antiviral drugs appears to delay and reduce the development of drug resistance.

The results of the study may be expressed in a variety of ways. Some studies will look for changes in surrogate markers (CD4+ counts and viral load) while others may look for changes in clinical endpoints (disease progression or death). Some studies presented viral load results as a percentage of volunteers with undetectable virus. This means the amount of virus in their blood was below the ability of the test to detect (usually about 200 RNA copies/ml).

- d4T/ddI
76 previously untreated volunteers with CD4+ counts between 200 and 500 received combinations of d4T and ddI. The mean baseline CD4+ count was 325. 26 volunteers have completed one year of treatment so far with a mean reduction in viral load of 1.8 logs and a mean increase in CD4+ of 141 cells. The reductions in viral load peaked at week 28 at 2.8 logs.

- Hydroxyurea/ddI
40 volunteers with CD4+ counts less than 250 received ddI and hydroxyurea for 24 weeks. There was a mean decrease in viral load of 1.0 logs sustained throughout the 24 weeks of the study but no significant increase in CD4+ cells.

In another study of hydroxyurea and ddI, 7 volunteers were treated for almost one year. Three of the volunteers had AIDS and 50% had previously been treated. All patients experienced a sustained reduction in viral load of 1.0 logs.

A third study of hydroxyurea and ddI treated 10 asymptomatic volunteers for one year. All the volunteers started with more than 189 CD4+ cells. After one year 60% of the volunteers had undetectable viral loads and a mean increase of 235 CD4+ cells. The other 40% had a mean reduction in viral load of 1.69 logs and a mean increase of 53 CD4+ cells.

- AZT/ddI/nevirapine
39 previously untreated, AIDS free volunteers with CD4+ counts between 200 and 600 were treated with AZT/ddI/nevirapine for one year. 60% of the volunteers had undetectable viral loads after one year of treatment. The mean reduction in viral load was 1.5 logs and the mean increase in CD4+ was 150 cells at one year. The peak reduction in viral load was greater than 2 logs about 4 weeks after starting the study.

- AZT/3TC/indinavir
Ninety-one subjects who had previously used AZT and/or 3TC received either AZT/3TC, indinavir alone or indinavir/AZT/3TC all in standard doses (indinavir 2.4 g/day). The average CD4+ cell count was 144 at the start of the study. Those subjects receiving indinavir alone or in combination had their CD4+ cell counts rise by 100 cells. Those subjects not receiving indinavir had their CD4+ cell counts increase by 40 cells. Viral load fell to 1/100th of its pre-study level among those who received indinavir (a 2 log decrease).

- 5-drug cocktail
Researchers used 6 subjects who had become HIV+ within the past 6 months and gave them standard doses of AZT, ddC, ddI and interferon-alpha; some also received 3TC. Viral load fell to 1/1,000 of its pre-treatment level (a 3 log decrease). One subject has normal levels of CD4+ cells and his viral load was less than 12 copies/ml.

- Ritonavir - effect on survival
Researchers conducted a placebo-controlled study using over 1,000 subjects with AIDS, some of whom received ritonavir 600 mg twice daily (1,200 mg/day). All subjects had less than 101 CD4+ cells. By the 6th month of the study 4% of subjects on ritonavir had died, compared to 8% of subjects who received placebo. Viral load fell to 1/10th its pre-study level and CD4+ cell counts increased by about 50 more cells.

- Saquinavir & d4T
Researchers gave 14 subjects with AIDS d4T 80 mg/day and saquinavir 1,800 mg/day. Their average CD4+ cell count climbed from 33 to 65 cells during the first month and then to 90 cells in the second month. Viral load fell to 1/100 th of its pre-study level during the first month but then rose to 1/10 th of its pre-study level by the second month.

- AZT/ddC/ritonavir
17 previously untreated volunteers with CD4+ counts between 50 and 250 were treated with AZT/ddC/ritonavir for 60 weeks. Volunteers started with mean 170 CD4+ cells. 60% of the volunteers had undetectable virus at 60 weeks. The mean reduction in viral load was 1.9 logs and the mean increase in CD4+ was 168 cells.

- Saquinavir/ritonavir
43 previously treated volunteers with CD4+ counts between 100 and 500 completed 6 weeks of treatment with saquinavir and ritonavir. The median decrease in viral load was 2.4 logs and the median increase in CD4+ was 98 cells.

Disclaimer
The Community AIDS Treatment Information Exchange (CATIE) provides information resources to help people living with HIV/AIDS who wish to manage their own health care in partnership with their care providers. We do not recommend or advocate particular treatments and we urge users to consult as broad a range of sources as possible. While we update our material regularly, users should be aware that information changes rapidly. Additional information may be available from CATIE at 1-800-263-1638 or at our website at http://www.catie.ca. Users relying on the information do so entirely at their own risk. Neither CATIE nor Health Canada accept responsibility for any damage that may result from the use or misuse of this information. Decisions about particular treatments should be made in consultation with a health care professional knowledgeable about HIV-related illnesses and the treatments in question.

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