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Levels of Evidence Based on the Oxford Centre for Evidence-Based Medicine (CEBM) Scale

Levels of Evidence Based on the Oxford Centre for Evidence-Based Medicine (CEBM) Scale

The concept of Levels of Evidence (LoE) is a widely used framework in medical statistics to assess the strength and reliability of research findings. LoE systems typically assign studies to hierarchical levels based on their study design, methodological rigor, and potential for bias. This hierarchical arrangement is intended to guide clinicians and researchers in making informed decisions about the applicability of research findings to clinical practice.


One of the most widely recognized LoE systems is the Oxford Centre for Evidence-Based Medicine (CEBM) scale, which categorizes studies into five levels


Level (CEBM)Type of EvidenceDescription
Level 1Systematic Reviews and Meta-Analyses of Randomized Controlled Trials (RCTs)Pools data from multiple RCTs, providing the highest quality evidence. These studies minimize bias and provide precise estimates of treatment effects.
Level 2Single Randomized Controlled TrialsIndividual studies that use random allocation to assign participants to treatment or control groups. They offer strong evidence but can vary in quality and size.
Level 3Non-Randomized Controlled TrialsControlled trials without randomization. These studies are more prone to bias compared to RCTs but can still provide valuable evidence, especially when RCTs are not feasible.
Level 4Cohort Studies and Case-Control StudiesObservational studies where cohort...

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