What are the levels of evidence in the European Association of Urology (EAU) guidelines?

EAU Guidelines Levels of Evidence

The European Association of Urology (EAU) uses a hierarchical evidence grading system with four main levels (1a through 4), where Level 1a represents the highest quality evidence from meta-analyses of randomized controlled trials, and Level 4 represents the lowest quality evidence from expert opinion. 1

EAU Evidence Level Classification

The EAU evidence hierarchy is structured as follows:

Level 1: Highest Quality Evidence

• Level 1a: Evidence obtained from meta-analysis of randomized controlled trials 1
• Level 1b: Evidence obtained from at least one randomized controlled trial 1

Level 2: Controlled Studies

• Level 2a: Evidence obtained from one well-designed controlled study without randomization 1
• Level 2b: Evidence obtained from at least one other type of well-designed quasi-experimental study 1

Level 3: Observational Studies

• Level 3: Evidence obtained from well-designed non-experimental studies, such as comparative studies, correlation studies, and case reports 1

Level 4: Expert Opinion

• Level 4: Evidence obtained from expert committee reports or opinions or clinical experience of respected authorities 1

Key Distinguishing Features of EAU Methodology

The EAU takes a more stringent approach to evidence grading compared to other major urological societies, particularly the American Urological Association (AUA). 1

Critical Differences from Other Guidelines:

• EAU reserves its highest evidence level (Level 1) exclusively for meta-analyses of RCTs or well-designed individual RCTs, unlike the AUA which includes "strong observational studies" such as cohort and case-control studies in its highest grade 1
• Well-designed observational studies are graded as second-tier evidence at best (Level 3) in the EAU system 1
• The lowest non-expert opinion level (Level 3) is defined as "good-quality retrospective case-control studies" or "well-designed nonexperimental studies and case reports" 1

Recommendation Grading System

The EAU pairs evidence levels with recommendation strength:

Strong Recommendations

• Strong recommendations (for/against) are given when the advantages of interventions obviously outweigh the disadvantages or vice versa 1
• These can be generated from evidence Levels 1-4 depending on the certainty and balance of effects 1

Weak Recommendations

• Weak recommendations (for/against) are given when the advantages and disadvantages of interventions are uncertain or when evidence shows that advantages and disadvantages are equal 1
• Typically arise from Level 3-4 evidence or when no evidence exists 1

Modern GRADE Integration

The EAU has evolved to incorporate modified GRADE (Grading of Recommendations Assessment, Development, and Evaluation) methodology in recent guideline updates. 1, 2

• This framework integrates certainty of evidence with other essential elements including magnitude of effects, balance of desirable and undesirable consequences, patient values and preferences, equity, acceptability, and feasibility 1, 2
• Evidence certainty can be rated as high, moderate, low, or very low under the GRADE framework 2
• The modified GRADE approach allows for more nuanced recommendation development beyond simple evidence hierarchy 1, 2

Clinical Implications

In the absence of high-level evidence, EAU guidelines become more dependent on expert opinions ("eminence-based medicine"), leading to greater divergence from other international guidelines. 1