Table 2.

Levels of expert recommendations

Level of evidence	Description
A	Good scientific evidence suggests that the medical treatment confers clear benefits; it is recommended that physicians perform the medical treatment on patients
B	Existing evidence shows that the medical treatment can confer moderate benefits that outweigh its potential risks; physicians can recommend or perform the medical treatment on patients
C	Existing evidence shows that the medical treatment may have little benefit, or the benefit is close to the risk; physicians can selectively recommend and perform the medical treatment on patients according to their individual condition
D	Existing evidence shows that the medical treatment has no benefit, or its potential risks outweigh the benefits; it is not appropriate for physicians to perform the medical treatment on patients
I	There is a lack of scientific evidence, or existing evidence cannot be used to evaluate the benefits and risks of the medical treatment; physicians should help the patients understand the uncertainty of the medical treatment