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Evaluation of studies of treatment or prevention interventions
  1. Nicky Cullum, RN, PhD
  1. Centre for Evidence Based Nursing, Department of Health Studies University of York, York, UK

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In the first article in this series, we discussed how critical appraisal is an important step in evidence-based health care because some published healthcare research is too poor in quality to be safely applied to clinical practice. Critical appraisal is made easier by the availability of quality checklists, which can be used to appraise research studies systematically and efficiently. With practice, readers may no longer even need a checklist and should be able to decide whether an article is worth reading in a matter of moments.

Whether your clinical question is one of treatment, diagnosis, prognosis, or causation, there are 3 fundamental questions you should apply in deciding whether the research might help us to provide better care to our patients.1

Are the results of the study valid?

This question considers whether the results reported in the study are likely to reflect the true size and direction of treatment effect. Was the research conducted in such a way as to minimise bias and lead to accurate findings, or was it designed, conducted, or analysed in such a way as to increase the chances of an incorrect conclusion?

What were the results?

Once you have determined that the results are valid, it is important to gain an understanding of what the results really mean. If the new treatment is shown to be effective, how large is the effect? Is the effect clinically important? How precise is the treatment effect (another way of asking how likely it is that the effect is real and not a result of the play of chance)? The precision of a result is related to whether the study involved large numbers of people (which increases precision) or small numbers (which reduces precision).

Will the results help me in caring for my patients?

There are 2 concepts underlying this question. Firstly, you have to decide if the patients participating in the study are sufficiently similar to your patients, …

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