Reference 1

Level I Good quality evidence Systematic review of RCTs with
consistent findings
High quality individual RCT
Level II Limited quality patient
orientated evidence
Systematic review of lower quality
studies or studies with inconsistent
findings
Low quality clinical trial
Cohort studies
Case-control studies
Level III Other Consensus guidelines, extrapolations
from bench research, usual practice,
opinion, disease-oriented evidence
(intermediate or physiologic outcomes
only), or case series

[1] British Society for Paediatric and Adolescent Rheumatology. Guidelines for Non-steroidal anti- inflammatory drug (NSAIDs) use in Paediatric Rheumatology. 2005.