Researchers establish new enrollment criteria for African volunteers

Researchers from IAVI, the US Centers for Disease Control and Prevention (CDC), and the US Military HIV Research Program (USMHRP) recently presented results from a study at the AIDS Vaccine 2007 meeting in Seattle indicating that a new set of medical criteria should be used to screen potential volunteers for AIDS vaccine trials in East and Southern African populations. Several routine laboratory tests are conducted before a healthy individual can enroll in a preventive AIDS vaccine trial so that researchers can assess the background health of the potential volunteer (seeVAX March 2005 Primer on Understanding Clinical Research Studies). The results of these tests are then compared to a set of previously-established results known as reference ranges that define what is considered acceptable. Based on this some potential volunteers are excluded from the trial.

However, many of these reference ranges are based on research in populations in North America and Europe only. A two-year study involving approximately 5500 healthy individuals from Uganda, Kenya, Rwanda, and Zambia showed that, for some of the tests, what is considered a normal result can be different in a healthy African individual. In this study, researchers took blood samples from healthy, HIV-uninfected individuals and used these to evaluate different blood values and their kidney and liver functions.

Establishing reference ranges that are relevant to local populations could help improve the enrollment process for clinical trials, including those of AIDS vaccine candidates, because fewer potential volunteers would be unnecessarily excluded. This could drastically improve the speed and ease of enrolling volunteers.

In an AIDS vaccine trial previously conducted by USMHRP in Uganda, 58% of potential volunteers were unable to participate because their laboratory results were outside of the established reference ranges. When a second trial was conducted by USMHRP at the same site using the newly-established reference range for that population, researchers only excluded 23%.

Local reference ranges will also help researchers differentiate naturally-occurring laboratory abnormalities from any possible side-effects caused by the vaccine candidate or other intervention being tested. Africans often have different results for many standard laboratory tests due to their exposure to a greater number of parasites and pathogens, which affects the functioning of the immune system.