TableĀ 3

Grading system used in the 2001 British Thoracic Society (BTS) guideline on diagnostic flexible bronchoscopy

IaEvidence obtained from meta-analysis of RCTs
IbEvidence obtained from at least one RCT
IIaEvidence obtained from at least one well designed controlled study without randomisation
IIbEvidence obtained from at least one other type of well designed quasi-experimental study
IIIEvidence obtained from well designed non-experimental descriptive studies such as comparative studies, correlation studies and caseā€“controlled studies
IVEvidence obtained from expert committee reports of opinions and/or clinical experiences of respected authorities
GradeType of recommendation
A (Ia, Ib)Requires at least one RCT as part of a body of literature of overall good quality and consistency addressing the specific recommendation
B (IIa, IIb, III)Requires availability of well conducted clinical studies but no RCTs on the topic of recommendation
C (IV)Requires evidence from expert committee reports or opinions and/or clinical experience of respected authorities. Indicates absence of directly applicable studies of good quality
  • RCT, randomised controlled trial.