The European Association of Urology uses the following evaluation system:
Table 1: Level of Evidence*
|Level Type of Evidence|
|1a Evidence from meta-analyses of randomized trials|
|1b Evidence from at least one randomized trial|
|2a Evidence from a well-designed controlled trial without randomization|
|2b Evidence from at least another type of a well-designed semi-experimental study|
|3 Evidence from well-designed non-experimental studies such as comparative studies, correlation studies|
4 Evidence from specialized committees’ reports or opinions or clinical expert experiences
* Modification by Sackett et al (1))
It should be though noted that when rating guidelines, the relationship between the level of evidence and grade of recommendation is not directly proportional.
The existence of randomized trials may not correspond directly to grade A of recommendation when there are problems in the methodology or discrepancies between the published results.
Conversely, the lack of high level of evidence does not exclude a grade A recommendation as long as there is significant clinical experience and consent.
In addition, there may be specific cases where there cannot be any confirmatory studies for special or other reasons and in this case, clear instructions may be of great help for the reader. Whenever this occurs, it has been noted in the text with an asterisk as an "Upgrade upon agreement of a specialized group".
The quality of the underlying scientific evidence -though a very important factor- must be balanced against benefit, severity, values, preferences and costs.
Table 2: Grade of Recommendation
|Grade Nature of the Recommendations|
|Α Based on clinical studies of good quality that constantly examine the specific instructions and include|
|Β Based on well-organized clinical studies but not randomized clinical trials|
C Recommendation despite the lack of clinical studies of good quality
|* Modification by Sackett et al (1)|
1. Oxford Centre for Evidence –based Medicine Levels of Evidence (May 2009). Pro- duced by Bob Phillips, Chris Ball, Dave Sackett, Doug Badenoch, Sharon Straus, Brian Haynes, Martin Dawes since November 1998.[Access date March 2011] http://www.cebm.net/index.
2. Atkins D, Best D, Briss PA, et al; GRADE Working Group. Grading quality of evidence and strength of recommendations BMJ 2004 Jun 19;328(7454):1490 http://www.ncbi.nlm.nih.gov/
3. Guyatt GH, Oxman AD, Vist GE et al. GRADE: an emerging consensus on rat- ing quality of evidence and strength of recommendations. BMJ 2008;336(7650):924
4. Guyatt GH, Oxman AD, Kunz R et al; GRADE Working Group. Going from ev- idence to recommendations. BMJ 2008 May 10;336(7652):1049-51. http://www.bmj.com/content/