Table 1

Classification of the literature consulted, according to strength of evidence

Level of evidence for studies on intervention:


A1

systematic reviews that comprise at least several A2 quality trials whose results are consistent

A2

high-quality randomized comparative clinical trials (randomized, double-blind controlled trials) of sufficient size and consistency

B

randomized clinical trials of moderate quality or insufficient size, or other comparative trials (non-randomized, comparative cohort study, patient control study)

C

non-comparative trials

D

opinions of experts, such as project group members


Level of evidence for conclusions:


1

at least one systematic review (A1) or two independent grade A2 studies

2

at least two independent grade B studies

3

at least one grade A2, B or C study

4

opinions of experts, such as project group members


Perez et al. BMC Neurology 2010 10:20   doi:10.1186/1471-2377-10-20

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