Intervention« Back to Glossary Index
A therapeutic alternative to standard or control therapy, which is often a new intervention, or different dose of a standard drug.
Experimental Therapy, Experimental Treatment
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Related Glossary Terms:
- Absolute Risk IncreaseThe absolute difference in the frequency of harmful outcomes between experimental and control groups, calculated as frequency of harmful outcomes in the experimental group minus the frequency of harmful outcomes in the control group. Typically used to describe a harmful exposure or intervention (e.g., if the frequency of adverse outcomes is 20% in treatment and 10% in control, the absolute risk increase would be 10% expressed as a percentage and 0.10 expressed as a proportion).
- Absolute Risk ReductionThe absolute difference (risk difference) in frequency of harmful outcomes between experimental and control groups, calculated as the frequency of harmful outcomes in the control group minus the frequency of harmful outcomes in the experimental group (CER–EER). Typically used to describe a beneficial exposure or intervention (e.g., if 20% of patients in the control group have an adverse event, as do 10% among treated patients, the ARR or risk difference would be 10% expressed as a percentage or 0.10 expressed as a proportion).
- Adjusted AnalysisAn adjusted analysis takes into account differences in prognostic factors (or baseline characteristics) between groups that may influence the outcome. For instance, when comparing an experimental and control intervention, if the experimental group is on average older, and thus at higher risk of an adverse outcome than the control group, the analysis adjusted for age will show a larger treatment effect than the unadjusted analysis.
- Allocation ConcealmentRandomization is concealed if the person who is making the decision about enrolling a patient is unaware of whether the next patient enrolled will be entered in the intervention or control group (using techniques such as central randomization, or sequentially numbered opaque sealed envelopes). If randomization is not concealed, patients with differing prognosis may be differentially recruited to treatment or control groups. Of particular concern, patients with better prognoses may tend to be preferentially enrolled in the active treatment arm resulting in exaggeration of the apparent benefit of the intervention (or even falsely concluding that the intervention is efficacious).
- Control GroupA group that does not receive the experimental intervention. In many studies, the control group receives either usual care or a placebo.