In vitro, animal, clinical: the stages of research

Why research goes in steps

An idea that looks promising in a tube may still be far from working in a living body. That is why research runs in fixed steps, from simple to complex. Each step filters out ideas that do not hold up, so only the strongest go on.

In vitro: the tube

In vitro literally means "in glass". Researchers test a compound on isolated cells or molecules, outside a living body. This is fast and cheap, and ideal for studying a mechanism. The drawback is clear: a cell in a dish is not a person. What happens there does not automatically predict what happens in a body.

Animal research: a living system

The next step is a study in animals, often mice or rats. Now the compound sits in a complete body, with a bloodstream, organs and a metabolism. That gives far more information than a tube. Still, a mouse differs from a human in important ways, so these results too do not automatically apply to people.

Clinical research: in people

Only when the earlier steps give enough confidence does research in people follow. That is called clinical research, and it moves through phases of its own.

• Phase 1 mainly looks at safety, in a small group.
• Phase 2 investigates whether there is an effect and in what range it occurs.
• Phase 3 tests that effect in a large group and compares against a control or placebo.

What does this mean when you read a study?

Always check first which stage a study is in. A striking result in cells is interesting, but it is a beginning, not an endpoint. A large phase 3 study in people carries far more weight. In our source library, every study lists its stage, so you can see at a glance how strong the evidence is.