Several key concepts are important in research.

Trial question – the hypothesis

This is the idea or theory that the trial aims to either prove or disprove.

Every trial or study needs to start with a question. For example:

• Is something happening?” ie does smoking/diet/exercise affect health? or ‘Do bone get more brittle as we age’?
• Can doing something improve health?
• Is one treatment better than (or as good as) another

Primary endpoint

The primary endpoint is the main way that the results of a trial will be assessed. It should be decided in the study design before any patients are enrolled.

A primary endpoint decides what level of evidence or results will be accepted to prove or disprove the study question. The choice of endpoints can determine whether the final results are going to be useful.

For example, with a new drug, the primary endpoint is often the percentage of people who have an undetectable viral load at a certain point. This could be 8 weeks for an early effect or 48 weeks for a longer effect.

But it could also be the average drop in viral load or the average increase in CD4 count. Or a direct measure of health in how many people see improved or reduced health.

Secondary endpoints

Secondary endpoints can look at everything else.

• Safety of a drug, side effects
• Impact on CD4 count
• Impact on quality of life
• Cost-effectiveness of treatment and many other factors

Community involvement in trial design can help ensure that important secondary endpoints are included when the study is first planned.