Table 1

Relationship between study quality and source of evidence, LoE, and grades of recommendation

Study typeStudy quality assessmentsLoEGrade of recommendation
(based on overall LoE, considering balance of clinical practice information and evidence)
Statistical analyses and patient follow-up assessmentAllocation concealment*Jadad scoresAdditional assessment of overall study quality required to judge LoE
Systematic review with homogeneous resultsNANANANA1A
RCTStatistics reported and >80% follow-upANDA(15)NA1A
(based on two or more studies or a single, large, well-designed study)
OR
B(35)NA
OR
B(1–2)Yes
RCTStatistics not reported or questionable or <80% follow-upAND/ORB(1–2)Yes2B
(or extrapolation from one procedure-specific
LoE 1 study)
OR
C(15)NA
OR
D15)NA
Non-systematic review, cohort study, case study (eg, adverse effects)NANA3C
Clinical practice information (expert opinion); inconsistent evidenceNANA4D
  • *Allocation concealment is given as A adequate, B unclear, C inadequate, and D not used.

  • LoE, level of evidence; NA, not applicable; RCT, randomized controlled trial.