Table 1

Levels of evidence (adapted and modified from van Tulder et al [33])

Strong
Consistent findings among multiple high-quality RCTs
Moderate
Consistent findings among multiple low-quality RCTs and/or one high-quality RCT
Limited
One low-quality RCT
Conflicting
Inconsistent findings among multiple trials
No evidence
No RCTs

Anttila et al. BMC Pediatrics 2008 8:14   doi:10.1186/1471-2431-8-14