Intended for healthcare professionals

Education And Debate

How to read a paper: Assessing the methodological quality of published papers

BMJ 1997; 315 doi: (Published 02 August 1997) Cite this as: BMJ 1997;315:305
  1. Trisha Greenhalgh (, senior lecturera
  1. a Unit for Evidence-Based Practice and Policy, Department of Primary Care and Population Sciences, University College London Medical School/Royal Free Hospital School of Medicine, Whittington Hospital, London N19 5NF
  1. Correspondence to


    Before changing your practice in the light of a published research paper, you should decide whether the methods used were valid. This article considers five essential questions that should form the basis of your decision.

    Question 1: Was the study original?

    Only a tiny proportion of medical research breaks entirely new ground, and an equally tiny proportion repeats exactly the steps of previous workers. The vast majority of research studies will tell us, at best, that a particular hypothesis is slightly more or less likely to be correct than it was before we added our piece to the wider jigsaw. Hence, it may be perfectly valid to do a study which is, on the face of it, “unoriginal.” Indeed, the whole science of meta-analysis depends on the literature containing more than one study that has addressed a question in much the same way.

    The practical question to ask, then, about a new piece of research is not “Has anyone ever done a similar study?” but “Does this new research add to the literature in any way?” For example:

    • Is this study bigger, continued for longer, or otherwise more substantial than the previous one(s)?

    • Is the methodology of this study any more rigorous (in particular, does it address any specific methodological criticisms of previous studies)?

    • Will the numerical results of this study add significantly to a meta-analysis of previous studies?

    • Is the population that was studied different in any way (has the study looked at different ages, sex, or ethnic groups than previous studies)?

    • Is the clinical issue addressed of sufficient importance, and is there sufficient doubt in the minds of the public or key decision makers, to make new evidence “politically” desirable even when it is not strictly scientifically necessary?

    Question 2: Whom is the study about?

    Before assuming that the results of a paper are applicable to your own practice, ask yourself …

    View Full Text

    Log in

    Log in through your institution


    * For online subscription