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Gripping the Evidence using Critical Appraisal Skills

CASP (Critical Appraisal Skills Programme) helps people develop the skills they need to appraise evidence affecting important local purchasing decisions. CASP workshops bring together a multi-disciplinary group of people such as GPs, consumers, purchasers and providers, which promotes collaboration within districts and develops a common desire to work together to get research evidence of effectiveness into practice.

Why GRiPP the evidence?

For the last 15 years, governments world-wide have struggled to contain the costs of health services and to use their available resources more efficiently. As policy makers grappled with ways to achieve this goal the emphasis focused on cost containment and the debate about effectiveness took second place [1].

In 1993 the Minister of Health in England identified `a sound knowledge base' as one of seven `stepping stones' to successful purchasing. This means purchasers must be able to assess the effectiveness and efficiency of medical interventions so that resources can be used to maximise the health gain of the population. That is, they must understand the benefits, costs and adverse effects of the services which they commission.

This task is made all the more urgent by Professor Eddy's estimate that only 15% of the medical interventions that we carry out in the NHS have been proved to be effective in improving patients' health [2]. Even where interventions have been shown to be effective, their translation into clinical practice can take decades, for example the use of steroids in pre-term labour [3].

What is CASP?

Purchasers frequently use reviews of evidence to give them the information they need. 'Reviews' are papers which synthesise the results of primary studies and so make scientific research available to a wider audience. Reviews, however, can often be poorly conducted and can be misleading in their conclusions.

To help people make sense of evidence about effectiveness, the former Oxford RHA set up CASP. CASP is now part of the Anglia and Oxford Region's GRiPP (Getting Research into Practice and Purchasing) project. In developing methods of helping people appraise reviews of evidence, CASP has worked closely with the UK Cochrane Centre and McMaster University in Canada.

Finding and appraising evidence about the cost effectiveness of interventions are the first steps in Getting Research into Practice and Purchasing as the CASP logo depicts.


CASP aims to help people develop skills in appraising evidence about clinical effectiveness through multi-disciplinary workshops. CASP is co-ordinated by a team based in Oxford. Each county in the Anglia and Oxford Region has a CASP co-ordinator who liaises and plans the workshops with the core CASP team. These individuals work only part-time for CASP.

What are CASP workshops like?

The workshop format is based on experience from pilot workshops and is constantly evaluated and improved. Firstly, there is an explanation about why critical appraisal skills are so important and how they fit into the GRiPP process. This is followed by an interactive talk in which the types of trials, reviews and meta-analysis, together with some basic definitions of epidemiological and statistical terms are explained. Participants then work in small groups to solve a problem scenario such as whether or not we should purchase ultra-sound screening for all pregnant women. Another scenario was whether or not dyspeptic patients who are positive for H. pylori should be treated with triple therapy. These problems are tackled by critically appraising a review article of evidence about the clinical effectiveness of that problem.

The workshops are usually multi-disciplinary which often leads to a lively debate about controversial issues. Opinions are tempered by having to critically appraise the evidence in a systematic way together.

So far 40 workshops have been held. The majority of participants (97%) have enjoyed the workshops and 90% feel that they are a good use of their time. People want more workshops in their areas and also to develop critical appraisal skills for other articles such as economic reviews and randomised control trials. They also want workshops on how to find evidence. Some participants are willing to help run future workshops and the CASP team holds training sessions for these individuals so that the workshops can be cascaded locally. We have helped people in South and West Region to run workshops and we liaise with North Thames Region where similar work is going on. We are keen to work in other areas.

What do people get out of a CASP workshop?

Different people get different things from a CASP workshop. This is because critical appraisal is a process which people can use in accordance with their needs. Some people only require an awareness of the importance of finding and appraising evidence, others will actually need to acquire the skills of critically appraising evidence and a few will require skills to enable them to write literature reviews.

What are CASP's future plans?

Many more CASP workshops will be run in 1995. Most of these will be purchaser-based, but others are being run for consumer groups, researchers, policy makers, audit groups and board members of health authorities and NHS Trusts. It is hoped that many initiatives that plan to implement change will use CASP workshops as a springboard to successful evidence based change in practice.
Catherine Brogan, Ruairidh Milne

If you would like more information
please contact
Ruairidh Milne on 01865 226741
Anglia & Oxford Regional Health Authority
Old Road, Headington, Oxford.


  1. Drummond, F.D. Maynard, A. Purchasing and providing cost-effective health care. Churchill Livingstone 1993.
  2. Smith R . Where is the wisdom? British Medical Journal 1991 303: 798-9
  3. Crowley, P. Chalmers, I. Keirse, M.J.N.C. The effects of corticosteroid administration before preterm delivery: an overview. British Journal of Obstetrics & Gynaecology 1990 97: 11-25.
  • Cochrane, A.L. Effectiveness and efficiency: random reflections on health services. Nuffield Provincial Hospital Trust 1971.
  • Milne R, Chambers L. Assessing the scientific quality of review articles. Journal of Epidemiology and Community Health 1993 47: 169-170.

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