Appraise

5. Step 2: Appraise the quality of the study

The level of evidence (Step 1) is a good indicator of how bias-prone the study design is likely to be.

In most instances, however, there is overlap between the quality of papers in the different levels of evidence. For example, when assessing a treatment, a well-designed cohort study may provide better evidence than a poorly designed randomised controlled trial.

From a practical point of view, when reading papers, you should focus on the major issues that determine the quality of information and decide whether you agree or disagree with aspects of the study e.g. design, information content, objectivity, overall validity and the conclusions. But first, let’s think about the statistics that might be in the paper.