According to WHO handbook for Guidelines we used the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach to assess the quality of a body of evidence, develop and report recommendations. GRADE methods are used by WHO because these represent internationally agreed standards for making transparent recommendations. Detailed information on GRADE is available through the GRC secretariat and on the following sites:
■ GRADE working group: http://www.gradeworkingroup.org
■ GRADE online training modules: http://cebgrade.mcmaster.ca/ ■ GRADE profile software: http://ims.cochrane.org/revman/gradeproTable 1 Quality of evidence in GRADE
Table 2 Significance of the four levels of evidence
Table 3 Factors that determine How to upgrade or downgrade the quality of evidence