Release Date: November 6, 2017
Category: Scientific Writing
Author: Katherine S., Ph.D., E.L.S.
In Part I, we discussed how to define your aim for a systematic review. In Part II, we defined your inclusion and exclusion criteria. In Part III, we conducted your search. In Part IV, we screened your articles and extracted the data.
I notice that there isn’t anything in the inclusion criteria about whether the study is good or not.
Excellent point, which is why you will need bias assessments. Bias assessments are important because they will help both you and your readers determine how reliable the included data are. Study bias is something that can occur in any study, including RCTs. The Cochrane Collaboration categorizes study bias into six categories (Chapter 8; http://handbook.cochrane.org/).
The Cochrane Collaboration has developed a tool to determine the overall risk of bias. A study is judged as having “low risk of bias,” “high risk of bias,” or “unclear risk of bias” in each of the six categories. A description of judgement criteria and how to score them is provided in Table 8.5.d of the Cochrane Collaboration Handbook, and different methods for presenting bias data are provided in Section 8.6. Scoring bias is another co-author activity. You and your fellow postdoc Anjali will need to score the risk of bias separately and compare your scores to make sure they match. If they don’t, you should talk it out until you both agree on the scores.
Anjali and I talked it out and ran the numbers. Everything looks good here. Can we get to the part where we actually compare studies now?
Yes, you can finally compare your studies. We’ll get into that in our next article, “Writing a Systematic Review Part VI: Comparing Studies.”
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