A Critically Appraised Topic (CAT) is a form of summarised evidence that tries to present an answer to a specified clinical question. A CAT is different to a systematic review or meta-analysis as the intention is not to systematically seek out all the evidence on a topic, but to look for the best available evidence and quickly come up with an answer. A CAT might be appropriate where there was no national guidance, but is not robust on its own to override existing national guidance.

A CAT starts with a well-defined clinical question that is relevant, well-structured and answerable. This then needs to be translated into a search question using a framework such as PICO (Patient or problem, Intervention or exposure, Comparison or control, Outcome(s)).

For a therapy questions, PICO would consist of the patient's disease or condition, a therapeutic intervention (for example a drug, surgical intervention, or medical advice). The comparison might be standard care, another intervention, or a placebo, and the outcome might be, for example, reduced mortality rate, complications, or disease recurrence.

The P (Patient or problem) may also include information about the population group (for example, older people, or women).

For example, the question ‘In a patient with acute bronchitis, do antibiotics reduce sputum production?’ could be put into a PICO framework as:

• P patients with acute bronchitis
• I antibiotics
• C none (it’s not always necessary to have a comparison)
• O reduction in sputum production

The PICO framework aids searching in databases, by allowing you to search for each concept separately using thesaurus and free-text terms to cover synonyms and variant spellings, and then combine the searches together to find research that covers all the concepts.

Since most CATs are related to therapy questions, the most appropriate study design would be an existing systematic review, or randomised controlled trials (RCTs) and these could be found in databases such as the Cochrane Library, Medline, EMBASE and CINAHL. Search filters are available to help limit the search to systematic reviews or RCTs.

Library staff are happy to either provide training and assistance on how to search these databases, or can carry out evidence searches on your behalf.

Once suitable articles have been found, they need to be appraised for their validity, and the CASP checklists are a good way to do this. There are different checklists available different types of evidence, and each one asks the most pertinent questions for that type of research.

The final stage is to summarise the evidence to come up with an answer to the clinical question initially posed, or a clinical ‘bottom line’.

Library staff are happy to support the development of CATs through suggesting suitable search terms or translating a clinical question into PICO, selecting databases, and providing critical appraisal resources, and we can point you in the direction of further resources.

When looking at service development or improvement, the evidence can seem quite limited. In many cases other people may have implemented new ideas or services, but not written it up for publication in a journal.

The sources below provide case studies and examples of improvements or innovations, and may be useful as a way of learning from other people's experiences or getting ideas to implement in practice. It's not an exhaustive list and case studies will be available in other sources, such as individual Trust's websites.

Library staff can also find evidence to support you in developing services or innovations, and we offer an evidence search service.

Academy of Fabulous Stuff

Describes itself as ‘A social movement for sharing Health & Social Care Ideas, services and solutions that work’. Includes informal case studies of new innovations or ideas. The quality of reporting varies.

eWIN Workforce Information Network

eWIN is the NHS workforce information network designed to enable improvements in workforce development, efficiency and productivity.

To search, visit the Tools and Resources page, enter your search terms and select ‘Case Study’ before running the search.

Health Foundation

An independent charity committed to bringing about better health and health care for people in the UK. To find case studies, run a search and filter to ‘Improvement projects’.

NHS Confederation

Membership body that brings together and speaks on behalf of all organisations that plan, commission and provide NHS services.

To find case studies, run a search and filter to ‘Case studies’ (under ‘Category’) then click ‘Apply Filters’.

NHS England

Search the publications database, and filter to ‘Case studies’. This is a very small collection.

NHS Improvement

Visit the Resources page, run a search and filter to ‘Shared Learning’.

NHS Improvement and NHS England have merged so this website may change, but new resources are still being added as of February 2020.

NICE Local Practice Case Studies

A number of case studies around implementing NICE Guidance in practice.

If you're searching for systematic reviews of evidence, you may find Epistemonikos a useful resource. Unlike the Cochrane Library, this contains systematic reviews from many sources (it does also contain some primary research articles that have been included in the reviews, but the main focus is systematic reviews).

Systematic reviews are an excellent source of high-quality evidence, and should use a clearly formulated question and systematic and explicit methods to identify, select, and critically appraise relevant research, and collect and analyse data from the studies that are included in the review.

While most of the systematic reviews included will be included in other sources such as Medline and EMBASE, they are not always easy to locate (though we have added some search filters to the Knowledge Navigator page to make this easier).

We've added Epistemonikos to the Systematic Review section of our Knowledge Navigator, where you'll find useful guidance and sources for locating many different types of evidence. Alternatively, why not simply ask us to conduct an evidence search for you?.