Table 1:

Criteria for assigning grade of evidence and strength of recommendations

Quality of evidence	Type of clinical study	Consistency of results
A = High	Randomized trial without important limitations	Considerable confidence in the estimate of effect
B = Moderate	Randomized trial with important limitations or exceptionally observational studies with strong evidence	Further research likely to have impact on the confidence in estimate, may change estimate
C = Low	Observational studies or case series	Further research is very likely to have impact on confidence, likely to change the estimate
Strength of recommendations	Balance between benefits and harms
1 = Strong	Certainty of imbalance
2 = Weak	Uncertainty of imbalance

The grading scheme classifies the quality of evidence as high (grade A), moderate (grade B), or low (grade C) according to the study design and to the consistency of results. The strength of recommendations was further classified as either strong (1) or weak (2) according to the balance between desirable and undesirable outcomes. Strong recommendations (1) are made when there is confidence that the benefits either do or do not outweigh the harm and costs of treatment. Where the magnitude of benefit or not is less certain, a weaker (1) recommendation is made. Grade I recommendations can be applied uniformly to most patients, whereas grade II recommendations require a more individualized application