Tools for assessing quality and risk of bias by levels of evidence

Sun Mi Lim, Ein Soon Shin, Sun Hee Lee, Kyung Hwa Seo, Yu Min Jung, Ji Eun Jang

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Tools for assessing methodological quality or risk of bias in randomized controlled trials (RCTs) and non-randomized studies (NRS) were reviewed. The van Tulder scale and Cochrane's assessment of risk of bias are the two most useful methodological quality evaluation tools for RCTs. Cochrane's tool includes sequence generation, allocation of sequence concealment, blinding, incomplete outcome data, selective outcome reporting, and other potential sources of bias. The Cochrane Collaboration Group recommends the Downs and Black instrument and the Newcastle-Ottawa Scale for evaluating the quality of NRS. In conclusion, this study offers useful information to physicians about tools for assessing the quality of evidence in clinical guidelines. Further research is needed to provide an essential core for evidence-based decision making regarding levels and/or grades of recommendations.

Original languageEnglish
Pages (from-to)419-429
Number of pages11
JournalJournal of the Korean Medical Association
Issue number4
StatePublished - 2011


  • Cochrane's tool
  • Downs and black instrument
  • Jadad's scale
  • Newcastle-Ottawa scale
  • Van tulder scale


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