There is a difference between the researchers when choosing the terms Effectiveness and Efficacy for Randomized Controlled Trials. While checking the previously published research studies the authors have used both. The existing literature states "Efficacy can be defined as the performance of an intervention under ideal and controlled circumstances, whereas effectiveness refers to its performance under ‘real-world' conditions". Therefore, which is the correct term for randomized controlled trials? Efficacy or Effectiveness. I kindly request the experts to share your expertise.
The terms are often used ambiguously and understood differently in different fields, but the distinction you provide is common. I would classify phase II and III RCTs as efficacy (effect)-studies, i.e., studies performed under optimal conditions (high concordance). In phase IV/post marketing /cohorts or in RCT:s where participants are randomized and followed up in registers it may be more appropriate talk about effectiveness.
A paper on the topic:
https://clinmedjournals.org/articles/iaphcm/international-archives-of-public-health-and-community-medicine-iaphcm-4-035.php?jid=iaphcm
Thank you Dr Per Lytsy for your expertise and for answering this important question. Most of the available literature describes the relationship between Efficacy or Effectiveness in drug trials (highly controlled studies like Phase I & II). What if the interventions provided are kind of behavioural modification like yoga, exercise, dietary modifications, education etc in a randomized controlled trial in hospital settings? Whether these types of studies also should use the word Efficacy or Effectiveness? Kindly share your thoughts on this
If it helps, I regard efficacy as a clinical pharmacology concept, ie: the compound has the intended effect at a receptor and therefore clinically. It is what we try to establish in Phase 1-2 trials. Effectiveness is a wider, more vague concept, something we aim to establish in Phase 3 trials.
Thank you very much Dr Andrew for sharing your expertise Andrew Sutton
Dear Ramesh Chandrababu. I think the same reasoning applies to interventions targeting behavioral modification. Within RCT:s participants consent and will be highly motivated and personal/staff will be educated and strictly follow protocols. Thus, the conditions will be favorable compared to when the same intervention is implemented in studies of routine care. So even though the line is not clear: in experimental prospectively controlled studies following protocols I would speak in term of effect/efficacy.
Well explained and agreed. Thank you very much for sharing your expertise Dr Per Lytsy
We have used the word efficacy for some nutrient media that are used in the Microbiology and Public Health laboratory for the isolation of organism from the clinical and environmental samples.
There is a validated tool to classify RCTs in an efficacy-effectiveness continuum. It is called the RITES tool (Wieland et al., 2018) https://doi.org/10.1016%2Fj.jclinepi.2017.01.010
It was developed through a Delphi study (with Cochrane members), pilot-tested and further validated. I recommend reading this report. Very interesting.
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