Table 1 Overview of the three self-controlled methods
Methods | Effect measures | Study populations | Information used in analysisa | Main assumptions |
|---|---|---|---|---|
Self-controlled case series | Incident rate ratio | Case patients who experienced at least one event during each observation period | Every exposure and every event for each case patient | Events do not alter the probability of subsequent exposure and events. |
Case-crossover design | (Exposure) odds ratio | Case patients who experienced at least one event during each observation period | Every exposure and the first event for each case patient | There are no time-trends in the occurrence of exposure. |
Sequence symmetry analysis | Adjusted sequence ratio | Case patients who experienced at least one exposure or one event during each observation period | The first exposure and first event for the study population | Events do not alter the probability of subsequent exposure. Trends in the occurrence of exposure and events are similar to those for the study population. |