TABLE 1.

Classification and definition of evidence quality in these guidelines

Evidence level	Definition
High (A)	It is quite certain that the observed value is close to the true value
Moderate (B)	Moderate confidence in the observed value: the observed value may be close to the true value, but it may also be quite different
Low (C)	Limited grasp of the observed value: the observed value may be quite different from the true value
Very low (D)	There is little certainty about the observed value: there may be a great difference between the observed value and the true value