Every trial has strict rules about who can join, called inclusion and exclusion criteria. Inclusion criteria are what you need to have or be in order to join the trial. For example, you may need to have a T4 cell count within a certain range, or be above or below a certain age. Exclusion criteria are things that will keep you out of the trial - for instance, you can not have certain illnesses or take certain treatments while in the trial.
If a particular condition is to be treated or prevented, the inclusion criteria are meant to bring in people who have or are likely to get that condition. The exclusion criteria are intended to keep out people who are at greatest risk of harm from the experimental treatment. In practice, the inclusion and exclusion criteria have sometimes been used unfairly to prevent people from participating in a clinical trial.
Pregnant women and drug users are often kept out of trials. Women may have to use birth control because the effects of an experimental treatment on a fetus are unknown, or are suspected to be harmful. Drug companies are unwilling to take the risk of being sued and therefore try to keep out women who do not use birth control. It’s important that women be included in clinical trials, because women’s bodies are different from men’s and may require different doses and types of treatment. More research is needed on treatments for diseases like cervical dysplasia and cancer, which are more common and harder to treat in HIV-positive women.
The relationships between HIV and cervical cancer, and HIV and PID, also need further research. In general, not enough is known about how AIDS develops in women and in children.
Drug users are often kept out of trials because it’s hard for researchers to know what they’re taking (since most street drugs are not pure). They may also be seen as unreliable and in poor health. However, more information is needed on drug use and HIV.