1) Clinical trials

• Randomized controlled trials

• Non-randomized interventional studies

• Device trials and procedural trials

• Drug and biologic studies

• Behavioral and digital health interventions

• Pragmatic and cluster trials

2) Observational studies

• Prospective cohort studies

• Case-control studies

• Cross-sectional studies with predefined outcomes

• Registry-based observational research

• Natural history studies

3) Systematic reviews and meta-analyses

• Systematic reviews with predefined protocol

• Meta-analyses

• Network meta-analyses

• Umbrella reviews

• Scoping reviews with structured methodology

Registration should occur before data extraction begins.

4) Case reports and case series

• Single case reports with structured objective

• Case series with predefined inclusion criteria

• Rare disease or rare complication reports

Registration is encouraged to document intent, predefined outcomes, and ethical oversight.

5) Diagnostic and prognostic studies

• Diagnostic accuracy studies

• Validation of prediction models

• Biomarker validation studies

• Artificial intelligence and algorithm validation

6) Quality improvement and service evaluations

• Prospective quality improvement projects

• Implementation science studies

• Structured service evaluations with predefined endpoints

7) Secondary data and database studies

• Predefined analyses of existing datasets

• Registry-based secondary analyses

• Administrative database studies with predefined outcomes

What does not typically require registration

• Narrative reviews without predefined methodology

• Editorials and opinion pieces

• Letters to the editor

• Educational material without research objectives