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Evidence-Based Medicine

Spot Knowledge 

  • Definition: Integration of best research evidence + clinical expertise + patient values

  • Goal: Maximise quality & duration of life, improve decision-making

🔄 EBM 5 Steps

  1. Formulate clinical question

  2. Search for evidence

  3. Critically appraise evidence

  4. Apply to practice

  5. Evaluate outcome

Evidence-Based Medicine: Definition, Process, and Levels of Evidence


Definition and Purpose


Evidence-based medicine (EBM) is an approach that integrates clinical expertise with the best available evidence from systematic research. The aim is to maximize both the quality and duration of patients’ lives. This approach emphasizes the integration of empirical evidence, clinical experience, and patient values.


Fundamental Steps


The EBM process consists of five stages:

  1. Formulating      an answerable clinical question.

  2. Identifying      and retrieving the evidence.

  3. Critical      appraisal of the evidence.

  4. Integrating      the evidence into clinical practice.

  5. Evaluating      the effectiveness and efficiency of the application.

The appraisal of evidence is not limited to randomized controlled trials and meta-analyses. Other study designs presenting consistent findings may also contribute to clinical practice. Studies are classified according to their quality and reliability.


Levels of Evidence and Study Types

  1. Therapeutic      Studies

  • Level      I: High-quality randomized controlled trials (RCTs) or homogeneous      systematic reviews.

  • Level      II: Lower-quality RCTs, prospective comparative studies.

  • Level      III: Case-control studies, retrospective comparative studies.

  • Level      IV: Low-quality cohort studies or case series.

  • Level      V: Expert opinion.

  1. Prognostic      Studies

  • Level      I: High-quality prospective studies and systematic reviews thereof.

  • Level      II: Retrospective studies or lower-quality prospective studies.

  • Level      III: Case-control studies.

  • Level      IV: Case series.

  • Level      V: Expert opinion.

  1. Diagnostic      Studies

  • Level      I: Development of diagnostic criteria tested in consecutive series of      patients, validated against an appropriate “gold standard.”

  • Level      II–IV: Development of criteria tested in more limited samples or      against lower-quality standards.

  • Level      V: Expert opinion.

  1. Economic      and Decision Analyses

  • Level      I: Robust data from multiple sources, supported by sensitivity      analyses.

  • Level      II: Analyses based on limited data and resources.

  • Level      III–IV: Analyses based on weak assumptions or limited sensitivity      testing.

  • Level      V: Expert opinion.

Key Concepts in Evidence-Based Medicine


Frequently used concepts in EBM include:

  • Absolute      Risk Reduction (ARR): The difference in event rates between treatment      and control groups.

  • Relative      Risk Reduction (RRR): The proportional risk reduction achieved by the      intervention.

  • Number      Needed to Treat (NNT): The number of patients that must be treated to      prevent one adverse outcome.

  • Likelihood      ratios, sensitivity, specificity, positive and negative predictive values:     Indicators of diagnostic test performance.

  • Randomized      Controlled Trial (RCT): A design in which treatment and control groups      are assigned randomly, considered the strongest source of evidence.

  • Meta-analysis      and Systematic Review: Methods combining results from multiple studies      to generate stronger evidence.

  • Type      I error (α) and Type II error (β): The probabilities of false-positive      and false-negative results, respectively.

Clinical Relevance


The evidence-based approach provides guidance not only in treatment selection but also in diagnosis, prognosis, and health economics. The reliability of clinical decision-making depends on the level of evidence employed. High-quality studies offer clinicians stronger and more dependable guidance.


Conclusion
Evidence-based medicine grounds healthcare decision-making on a scientific basis. Its primary goal is to maximize patient benefit. The integration of clinical expertise, patient preferences, and robust scientific evidence constitutes the foundation of modern medical practice.


References

1. StatPearls. Evidence-Based Medicine. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan. PMID: 35412347.

2. Howick J, Chalmers I, Glasziou P, Greenhalgh T, Heneghan C, Liberati A, et al. The Oxford Levels of Evidence 2. Oxford Centre for Evidence-Based Medicine; 2011.

3. Puljak L. The difference between evidence-based medicine, evidence-informed practice, and evidence generation. J Clin Epidemiol. 2022;145:1–3. doi:10.1016/j.jclinepi.2021.12.002

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