Establishing a library of resources to help people understand key concepts in assessing treatment claims-The "Critical thinking and Appraisal Resource Library" (CARL)

PLoS One. 2017 Jul 24;12(7):e0178666. doi: 10.1371/journal.pone.0178666. eCollection 2017.


Background: People are frequently confronted with untrustworthy claims about the effects of treatments. Uncritical acceptance of these claims can lead to poor, and sometimes dangerous, treatment decisions, and wasted time and money. Resources to help people learn to think critically about treatment claims are scarce, and they are widely scattered. Furthermore, very few learning-resources have been assessed to see if they improve knowledge and behavior.

Objectives: Our objectives were to develop the Critical thinking and Appraisal Resource Library (CARL). This library was to be in the form of a database containing learning resources for those who are responsible for encouraging critical thinking about treatment claims, and was to be made available online. We wished to include resources for groups we identified as 'intermediaries' of knowledge, i.e. teachers of schoolchildren, undergraduates and graduates, for example those teaching evidence-based medicine, or those communicating treatment claims to the public. In selecting resources, we wished to draw particular attention to those resources that had been formally evaluated, for example, by the creators of the resource or independent research groups.

Methods: CARL was populated with learning-resources identified from a variety of sources-two previously developed but unmaintained inventories; systematic reviews of learning-interventions; online and database searches; and recommendations by members of the project group and its advisors. The learning-resources in CARL were organised by 'Key Concepts' needed to judge the trustworthiness of treatment claims, and were made available online by the James Lind Initiative in Testing Treatments interactive (TTi) English ( English also incorporated the database of Key Concepts and the Claim Evaluation Tools developed through the Informed Healthcare Choices (IHC) project (

Results: We have created a database of resources called CARL, which currently contains over 500 open-access learning-resources in a variety of formats: text, audio, video, webpages, cartoons, and lesson materials. These are aimed primarily at 'Intermediaries', that is, 'teachers', 'communicators', 'advisors', 'researchers', as well as for independent 'learners'. The resources included in CARL are currently accessible at

Conclusions: We hope that ready access to CARL will help to promote the critical thinking about treatment claims, needed to help improve healthcare choices.

MeSH terms

  • Databases, Factual*
  • Evidence-Based Medicine
  • Health Resources*
  • Humans
  • Learning
  • Libraries*
  • Thinking

Grants and funding

Funding was received from the National Institute for Health Research, UK (, by IC. The funders had no role in the study design, data collection or analysis, decision to publish or preparation of the manuscript. Funding was also received from Minervation Ltd. In the form of author’s salary for Douglas Badenoch. Minervation Ltd is a consulting contractor providing editorial, project management, web design and technical development services to the Testing Treatments project. There were no competing or commercial interests.