Self-controlled study overview — Self-controlled case series

Question

Define a transient exposure, acute event and within-person risk contrast.

Assess design assumptions

Assess event-dependent exposure, event-dependent observation and recurrence before committing to standard SCCS.

Identify cases

Identify event cases with reliable histories and retain unique-person and event counts separately.

Construct observation and risk periods

Construct nonoverlapping observation, risk, pre-exposure and baseline periods according to the protocol.

Ascertain events

Ascertain event dates consistently and specify handling of recurrent or dependent events.

Compare within people

Estimate relative incidence within people with interval-duration offsets and time-varying adjustment.

Assess robustness

Vary justified windows and assumptions; use an appropriate extension or limit the question if standard conditions fail.

Report

Report the selected cases, periods, estimates and assumption limitations without extrapolating absolute population risk.

Self-controlled 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.