Table 3

Level of evidence

Level of evidence
# of studies
2004–2007
# of studies
up to 2003
total # studies
to June 2007

systematic reviews
1
1
2
RCT's
1
9
10
Observational
2
1
3
Descriptive
36
141
177
Conference abstracts
17
14
31
     RCT
0

5

5

     OBSERV
1

0

1

     DESC
16

9

25


Gotlib and Rupert Chiropractic & Osteopathy 2008 16:11   doi:10.1186/1746-1340-16-11