Efficacy is the benefit of an intervention gained under ideal conditions, such as in a randomised controlled trial.  ‘Ideal conditions’ refers to an experimental and controlled setting, where contextual factors (treatment administration, population characteristics, healthcare system characteristics) are fixed and balanced across the two (or more) study groups through randomisation, blinding and standardisation.  The design of the clinical trial is usually optimised to show the greatest benefit of the investigated intervention(s). Regulatory authorities are primarily interested in the balance of efficacy and harms (adverse effects) measured in clinical trials, whereas in health technology assessment the focus is on benefits that are achieved in usual practice, where the contextual factors are not fixed.


How to cite: Efficacy [online]. (2016). York; York Health Economics Consortium; 2016. https://yhec.co.uk/glossary/efficacy/


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