Interventional studies
Participants are assigned to one or more interventions so researchers can evaluate biomedical or health-related outcomes. Interventions may include medicines, devices, procedures or behavioural approaches.
The protocol defines objectives, endpoints, study design, safety monitoring and eligibility. Phases are mainly used for interventional drug development and should not be treated as a simple quality ranking.
Observational studies
Researchers assess outcomes in participants who are not assigned an intervention by the protocol. These studies may describe disease, treatment patterns, long-term outcomes or real-world practice.
Observational does not mean unimportant or risk-free. Consent, privacy and study-specific procedures still matter.
Read status and locations carefully
Recruiting, Not yet recruiting and Active, not recruiting describe different overall states. A location list may include sites that are no longer enrolling or have not opened.
Use the last update date as a freshness signal, then confirm availability with the named site or sponsor contact.
Quick answers
Frequently asked questions
Is an observational study a clinical trial?
It is clinical research, but it does not assign an intervention in the same way as an interventional trial.
Does a phase identify whether a study is suitable?
No. Phase describes a development stage; suitability depends on objectives, protocol criteria and clinical assessment.
Evidence base
Primary and authoritative sources
Use the linked source documents for professional or current interpretation.