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

   Table 2          Significance of        the      four    levels of        evidence    

Table  3          Factors          that     determine     How   to        upgrade        or            downgrade   the      quality           of        evidence