Rating Systems

Evidence-Based Practice: Systems to Rate the Strength of Scientific Evidence, AHRQ Publication No. 02-E016


This report is based on more than 100 reviewed sources of information on systems for assessing study quality and strength of evidence for systematic reviews and technology assessments. The report contains 19 systems which can be used in producing systematic reviews and other knowledge sources that are transparent for groups working with summaries, clinical practice guidelines, and other health-related policy advice. This information is for reference purposes only which was current when produced in 2002 and may now be outdated. However, the procedures and methods can be used with systematic reviews and technology assessments for identifying existing quality rating scales or checklists. The following systems have been used most frequently in evidence work conducted in the Academic Center for Evidence-Based Practice:

  1. Harris, R.P., Helfand, M., Woolf, S.H., Lohr, K.N., Mulrow, C.D., Teutsch, S.M. & Atkins, D. (2001). Current methods of the US Preventive Services Task Force: A review of the process. [Methods Work Group, Third US Preventive Services Task Force]. American Journal of Preventive Medicine, 20(3 Suppl), 21-35.
  2. Center for Evidence-Based Medicine (CEBM). (n.d.). Levels of evidence and grades of recommendations. Retrieved from http://www.cebm.net/index.aspx?o=1025.
  3. Stevens, K.R., McDuffie, K., & Clutter, P.C. (2009). Research and the mandate for evidence-based practice, quality, and patient safety. In M.A. Mateo & K.T. Kirchhoff (Eds.). Research for advanced practice nurses: From evidence to practice (chap. 3, pp. 43-70). New York: Springer Publishing Company.


Oxford Centre for Evidence-Based Medicine: Levels of Evidence (CEBM):
Located at the University of Oxford, England, the CEBM develops, teaches, and promotes evidence-based healthcare, providing support for physicians, nurses, and other healthcare professionals. CEBM concentrates on research and development, training for students and clinicians, and training the trainers to conduct research and development and teaching evidence-based medicine. Their website provides a comprehensive list of online EBM resources (http://www.cebm.net/index.aspx?o=1016), free evidence-based medicine tools (http://www.cebm.net/index.aspx?o=1023) and resources (http://www.cebm.net/index.aspx?o=1023) for the practice of EBM, and much more, such as links to the latest research (http://www.cebm.net/index.aspx?o=1744) and publications (http://www.cebm.net/index.aspx?o=1123).


A major resource for Evidence-Based Medicine is the 2011 revised CEBM Levels of Evidence (http://www.cebm.net/index.aspx?o=5653). The "levels", first introduced in 1998, have been newly revised in light of new concepts and data, and are set out as a series of searching "steps". While the steps (columns) give the likely "level" of evidence, the level selected will also depend on (1) the nature of the question and (2) the quality, quantity, and consistency of primary evidence found at that step. The Levels of Evidence table can be freely downloaded. http://www.cebm.net/index.aspx?o=1001.