Case-control overview — Case-control study

Question

Define the outcome, source population and exposure hypothesis.

Protocol

Prespecify case definitions, control sampling, exposure ascertainment and permissions.

Define source population

Identify the population in which a person would have been captured as a case if the outcome occurred.

Ascertain cases

Ascertain eligible cases and their index dates; distinguish incident from prevalent disease.

Sample controls

Sample controls from the appropriate source population or risk sets; controls need not be free of every disease.

Measure prior exposures

Measure exposures before comparable index dates using consistent procedures for cases and controls.

Analyze sampling design

Select a model compatible with sampling and matching; state what the estimated odds ratio represents.

Assess bias

Assess selection, recall, measurement and confounding concerns with justified sensitivity analyses.

Report

Report case and control recruitment separately, effect estimates with uncertainty, and sampling-dependent interpretation.

Case-control overview

End flow

Protocol and decision register

Record the protocol, approvals and registration where applicable. Preserve planned decisions and amendments separately from results.

Protocol and rationale evidence

Attach the rationale and dated protocol, retaining amendments. A study registry records study details; a disease registry contains health data. The HMA–EMA Catalogue of RWD studies is one option for relevant studies. Check eligibility and applicable requirements, and record an identifier and timing if registered. Registration does not imply randomization.