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A Simple Guide to Critical Appraisal

When I review a clinical trial, I ask myself a set of questions to help me understand how well I think the paper makes its case. This is something I have come up with on my own, after many years as a joural editor, educator and teacher of evidence-based practice. Of course, there exist many useful tools and instruments to help you do the same, but these seem to help me most.

  1. What is the question? I want to know the specific question the researcher is asking. This is not always as clear as you may think. The question helps determine what statistical analysis will be done.
  2. Did they account for all the patients? Patients drop out of studies. You need to account for this in some way, because the ones who drop out might be different from the ones who stay. Did the researchers conduct an intention-to-treat analysis?
  3. Were the outcomes assessed blind? Did the researchers ensure, as much as possible, that outcomes were assessed without knowledge of what treatment was received? In chiropractic studies, this may not always be possible.
  4. Are the outcomes clinically relevant? This is the difference between the so-called POEM (patient-oriented evidence that matters) and DOE (disease-oriented evidence). That is, do the outcomes have meaning to the patient (such as would be the case with pain or disability) as opposed to the researcher (who might look for a chance in Q angle in the knee, which means little to the patient).
  5. Were the treatments groups similar at baseline? This is usually indicated in table 1, in which the two (or more) groups are compared in terms of important demographic indicators such as age or gender breakdown. If, for example, the age of one group is 6 years older than the other, the results might be due to the age difference and not the treatment. The demographic table helps show the group similarities or differences.
  6. Was the design of the study described in detail? The old adage is, could another researcher be able to exactly replicate what was done in this study? That means the treatments should be described in detail; it is not enough to simply say that side-posture HVLA adjustments were given to the patient.
  7. Were the results interpreted for you? Did they in fact answer the question they asked? Did they place their answer into the context of past research?
  8. Did they describe the ethics of their study? Did they tell you if the study was approved by an ethics board and that participants gave informed consent.
  9. Was the sample size justified? Did they tell you why they chose the number of patients that were in the study?

These questions are a good start to looking at the study’s rigor.

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