Nested study overview — Nested case-control study

Question

Define the cohort-based outcome and why sampling exposure information is useful.

Define cohort

Specify cohort membership, baseline data, observation periods and incident case eligibility.

Follow outcomes

Ascertain events during follow-up and retain the population still at risk at each event time.

Form event-time risk sets

Construct each risk set using eligibility immediately before the case event.

Sample controls

Sample controls according to the protocol, allowing repeated selection and later case status when appropriate.

Ascertain exposures

Measure exposure using a comparable pre-index window within each sampled set.

Analyze matched sets

Use a model consistent with matching and sampling; retain identifiers and account for dependence where required.

Report

Report cohort size, incident cases, unique sampled people and sampling appearances as distinct quantities.

Nested study 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.