Core Outcome Sets: What They Are & Their Relevance to Research and KT

By Alexandra Korall

CHI KT Platform
Sep 25, 2018 · 5 min read

In this blog, we break down what a core outcome set is, explain why they are important, discuss how core outcome sets are meant to be used, and provide direction on where you can go to find out if a core outcome set exists in your field.

What are core outcome sets?

For those not familiar, outcomes are variables measured at the end of research studies using various instruments (like questionnaires or physical tests) to demonstrate whether an intervention or treatment was effective, and can include things like changes in a persons’ health status, improvements in efficiency of health care services, and so on. A core outcome set (COS) is a list of outcomes which experts have recommended that researchers should measure and report if they are undertaking a research study in a particular area [1]. These are not necessarily the only things a researcher should measure, but rather the ‘bare minimum’ or ‘core’ set of outcomes to be measured. Although related, core outcome sets, which specify the types of outcomes to measure and report, are not the same as core outcome measurement instrument sets, which specify how outcomes should be measured and reported [1].

More often than not, core outcome sets are accompanied by a core outcome measurement instrument set. For example, members of the Prevention of Falls Network Europe (ProFaNE) published a combined core outcome set and core outcome measurement instrument set for researchers planning randomized controlled trials in the area of fall injury prevention for older adults [2]. This combined core outcome and measurement instrument set recommended that researchers should measure and report the following outcomes in fall injury prevention trials: falls, fall injuries, physical activity, psychological consequences of falling, and health-related quality of life. It also contained recommendations on how to measure and report each of these outcomes.

Why are core outcome sets important?

Knowledge synthesis (which is core to KT) is a term used to describe the method of comparing, contrasting and combining results from individual studies and interpreting these results within the context of the global evidence [3]. Often this comes in the form of systematic reviews and meta-analyses that summarize evidence from multiple studies. Evidence generated from rigorous knowledge synthesis activities, like systematic reviews, are considered more useful for making important health decisions, as they are often less prone to bias than individual studies [3]. For example, studies may have recruited slightly different groups of individuals to participate, may have taken place in different geographic regions, and so on. These differences could influence the results of individual studies.

Frustration arises when studies measure and report different outcomes to examine the effectiveness of the same treatment or intervention. Like comparing apples to oranges, this makes it nearly impossible to give a conclusive recommendation about the effectiveness of the intervention or treatment, since the evidence can’t be properly combined. The ultimate goal of core outcome sets is to standardize outcome reporting across studies, so we can better compare and contrast the effectiveness of interventions or treatments across different contexts, circumstances and populations. This should ultimately allow healthcare consumers to make more informed health decisions, and facilitate our understanding of which interventions are worth implementing in real-world applications, practice, and policy.

In addition, outcome reporting bias or ‘publication bias’ — publishing specific outcomes, usually those with favourable results — is a pertinent issue in clinical trials [4], one which core outcome sets could help to resolve. Another important rationale for the use of core outcome sets is to ensure that reported outcomes reflect endpoints that are meaningful for service users (i.e. policy makers, patients, and the public). Through priority-setting exercises such as those used in the James Lind Alliance, involving patients and the public in selecting relevant outcomes (and even in developing core outcome sets) has resulted in the inclusion of outcomes that may not have even been considered by practitioners alone [5]. Though not yet studied, the use of core outcome sets may also help improve uptake by healthcare practitioners, through increased visibility and validity of measures and related behaviours used in knowledge translation and implementation research. It may also help KT practitioners to transfer findings of implementation research to various contexts with greater ease. Finally, standardized outcome reporting should help to reduce research waste, by increasing the relevance and applicability of findings.

How are core outcome sets meant to be used in research?

Presumably, there is greater potential to compare, contrast and combine findings of individual trials when researchers measure and report the entire collection of outcomes from the core outcome set in research studies. As already mentioned, researchers are neither encouraged nor expected to restrict their choice of outcomes in a research study to only those contained in a core outcome set [1]. Rather, there is an expectation that they will measure and report additional outcomes beyond those contained in the core outcome set. For example, other outcomes may be particularly relevant to specific populations or conditions, such as Patient-Reported Outcomes (PROs) and Patient-Reported Outcome Measures (PROMs) identified as important by people with a lived experience of a health condition though patient and public engagement activities.

Where can I look to find out whether a core outcome set exists or is under development in my field of research?

The Core Outcome Measurement in Effectiveness Trials (COMET) Initiative maintains a database of completed, ongoing and planned core outcome sets. The COMET database currently contains 1033 references, and they are continually updating their database. For more information, check out the COMET website at


  1. Williamson PR, et al. The COMET Handbook: version 1.0. Trials, 2017;18(Supp 3):280.
  2. Lamb SE, et al. Development of a Common Outcome Data Set for Fall Injury Prevention Trials: The Prevention of Falls Network Europe Consensus. J Am Geriatr Soc, 2005;53(9):1618–1622.
  3. Tetzlaff J, Tricco AC, Moher D. Knowledge Synthesis. In Knowledge Translation in Healthcare: Moving from Evidence to Practice, Sharon E. Straus, Jacqueline Tetroe, & Ian D. Graham (eds.). Chichester: John Wiley & Sons, 2013. 29–49.
  4. Dwan K, et al. Systematic review of the empirical evidence of study publication bias and outcome reporting bias. PLoS One, 2008;3(8).
  5. Williamson PR, et al. Developing core outcome sets for clinical trials: issues to consider. Trials, 2012;13:132.

About the Author

Alexandra Korall is a post-doctoral fellow in the Knowledge Translation platform at the George & Fay Yee Centre for Healthcare Innovation (CHI). Her current research focus includes identifying barriers and enablers to uptake of core outcome sets among researchers undertaking randomized controlled trials to examine interventions to prevent falls in older adults, and to identify barriers and enablers to uptake of patient, caregiver and clinician identified research priorities established using the James Lind Alliance methodology among health researchers and funding agencies in Canada.


Publishing bi-weekly, we focus on all things knowledge translation (KT) – synthesis, exchange, application & dissemination – from a health perspective. Topics include the science of KT, patient engagement, and media & dissemination.

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Know-do gaps. Integrated KT. Patient & public engagement. KT research. Multimedia tools & dissemination. And the occasional puppy.


Publishing bi-weekly, we focus on all things knowledge translation (KT) – synthesis, exchange, application & dissemination – from a health perspective. Topics include the science of KT, patient engagement, and media & dissemination.