Causal estimation scenario | Case study | Treatment changes adjusted for | Causal question being addressed |
---|---|---|---|
Interest in efficacy despite pragmatic trial design | |||
 | MRC hypertension trial | Addition of alternative treatments due to inadequate blood pressure control, or switches to alternative treatments due to side effects | Treatment efficacy in absence of treatment switches or additions |
 | SANAD trial | Withdrawal from randomised treatment, addition of alternative treatments, or switches to alternative treatments due to inadequate seizure control | Treatment efficacy in absence of treatment changes due to inadequate seizure control |
Trial protocol differs from practice | |||
 | Vitamin A trial | Non-receipt of trial drug due to failure of the drug distribution system | Treatment efficacy among those who would have complied with active treatment if randomised to receive it |
Contamination (control arm receives intervention) | |||
 | Honey trial | More extreme forms of treatment, such as antibiotics, surgery or radiotherapy Patient or clinician decision to switch from conventional dressings to honey | Treatment efficacy in absence of any treatment changes |
 | PACIFICO trial | Switches from standard to new treatment on disease progression | Treatment efficacy in absence of treatment switches from standard to new treatment on progression |
Interest in efficacy if taken as prescribed | |||
 | Coronary Drug Project | Failure to take treatment according to prescribed schedule | Treatment efficacy among those who complied with treatment protocol |