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L1 EBP Introduction to EBP

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aliasesL1 EBP Introduction to EBP

12 min read

Overview

This lecture introduces evidence-based practice (EBP): what it is, why good evidence matters for clinical decisions, how evidence is ranked and appraised, and the five-step process for applying it. It works through a single worked case, hydroxychloroquine for COVID-19, to show the whole process in action, from an initial mechanistic rationale through early observational data, a randomised controlled trial, and a Cochrane systematic review. It closes by placing EBP within the wider ELM curriculum and by introducing the ResearchSmart information-literacy course.

ResearchSmart (course logistics)

  • ResearchSmart is an online information-skills course (run by Christy Ballard, Librarian) developing research skills for study and practice.
  • Rationale: information literacy (acquiring, organising, analysing, evaluating and presenting information) is a graduate attribute, and is specifically needed for the Genetics Essay in Semester 2.
  • Structure: four topics, four quizzes, one evaluation, taking about two hours; each quiz must be passed at 100% to progress to the next topic (unlimited attempts).
  • Access: via MedMoodle (medschool.otago.ac.nz), open until 7:00pm Sunday 20 July 2025; completion is a Terms Requirement.

What is evidence-based practice?

  • Evidence-based medicine (EBM): “the conscientious, explicit, judicious and reasonable use of modern, best evidence in making decisions about the care of individual patients” (Masic et al, 2008).
  • Clinical decision-making is depicted as the overlap of three circles: patient values and choices, best available evidence, and clinical expertise; EBP sits at their intersection, not in evidence alone.
  • Dignity is part of what EBP must respect: patients are “knowers” who interpret their own reality, and disregarding that violates their dignity, a consideration that sits alongside the evidence itself when applying it to an individual (Abimbola, The Lancet, 2023).
  • Why best evidence matters: research findings evolve, you will likely need to do research during training, and patients (and non-patients) will ask you about health research they see in the news.
  • Consequences of practising without good evidence: ineffective treatments get used, treatments whose harms outweigh their benefits get given, existing effective interventions are missed, and expensive treatments may turn out to be no better than cheaper ones.

Clinical epidemiology: what different questions need

Different clinical questions map to different study designs:

  • Diagnostic accuracy (cross-sectional studies): does a positive test mean disease is present, does a negative test mean it is absent?
  • Descriptive cross-sectional or cohort studies: how common is the disease, and who is most likely to get it (incidence and prevalence)?
  • Cohort and case-control studies: what causes the disease?
  • Randomised controlled trials (intervention studies): is there a treatment, and does it cure disease, improve survival, improve quality of life, prevent/delay complications, or prevent/minimise spread? Is one treatment more effective than another? What are the harms of treatment?

Hierarchy of evidence

  • Pyramid of scientific evidence, lowest to highest: case reports/opinion papers/letters, animal trials and in vitro studies, cross-sectional studies, case-control studies, cohort studies, randomised controlled trials, meta-analyses and systematic reviews (highest).
  • Contrasted with sources that are not scientific evidence: YouTube videos, personal anecdotes, gut feelings, parental instincts, “some guy you know,” and websites such as Natural News, InfoWars, Natural Health Warriors, Collective Evolution, Green Med Info, Mercola.com and Whale.to.
  • Choice of study design depends on the research/clinical question: “no evidence ranking system or decision tool can be used without a healthy dose of judgment and thought” (Howick et al, OCEBM).
  • The Oxford Centre for Evidence-Based Medicine (OCEBM) 2011 Levels of Evidence table ranks evidence (Step 1, strongest, to Step 5, weakest) separately for each type of clinical question:
    • How common is the problem? Step 1: local/current random sample surveys or censuses. Step 2: systematic review of surveys matched to local circumstances. Step 3: local non-random sample. Step 4: case-series.
    • Diagnostic/monitoring test accuracy: Step 1: systematic review of cross-sectional studies with consistent reference standard and blinding. Step 2: individual such cross-sectional studies. Step 3: non-consecutive studies or inconsistent reference standards. Step 4: case-control studies or poor/non-independent reference standard. Step 5: mechanism-based reasoning.
    • Prognosis (what happens without added therapy): Step 1: systematic review of inception cohort studies. Step 2: inception cohort studies. Step 3: cohort study or control arm of an RCT. Step 4: case-series/case-control or poor-quality prognostic cohort study.
    • Treatment benefit: Step 1: systematic review of randomised trials or n-of-1 trials. Step 2: randomised trial or observational study with dramatic effect. Step 3: non-randomised controlled cohort/follow-up study. Step 4: case-series, case-control, or historically controlled studies. Step 5: mechanism-based reasoning.
    • Common treatment harms: Step 1: systematic review of randomised trials or of nested case-control studies, an n-of-1 trial, or observational study with dramatic effect. Step 2: individual randomised trial or (exceptionally) observational study with dramatic effect. Step 3: non-randomised controlled cohort/follow-up (post-marketing surveillance) study with sufficient numbers to rule out a common harm (sufficient follow-up duration for long-term harms). Step 4: case-series, case-control, or historically controlled studies. Step 5: mechanism-based reasoning.
    • Rare treatment harms: Step 1: systematic review of randomised trials or n-of-1 trial. Step 2: randomised trial or (exceptionally) observational study with dramatic effect. (Steps 3-5 not specified.)
    • Is a screening test worthwhile? Step 1: systematic review of randomised trials. Step 2: randomised trial. Step 3: non-randomised controlled cohort/follow-up study. Step 4: case-series, case-control, or historically controlled studies. Step 5: mechanism-based reasoning.
    • Footnotes: a level can be graded down for poor study quality, imprecision, indirectness (study PICO doesn’t match the question’s PICO), inconsistency between studies, or a very small absolute effect size; it can be graded up for a large or very large effect size. A systematic review is generally better than an individual study of the same design.

Five steps of evidence-based practice

  1. Formulate a clinical question: translate a clinical problem into an answerable question.
  2. Find the evidence: systematic searching for the best available evidence.
  3. Appraise the evidence: for validity and clinical usefulness.
  4. Apply the evidence: work out how the findings apply to your own practice.
  5. Evaluate performance: of the evidence-based decisions made.
  • Steps 3-4 (appraise/apply) require considering contextual and patient factors when applying evidence to an individual.
    (Akobeng AK, Principles of evidence-based medicine, 2005.)

Case study: hydroxychloroquine and COVID-19

  • Background on the drug: hydroxychloroquine is an antimalarial also used for inflammatory conditions (rheumatoid arthritis, lupus erythematosus), with rare adverse effects including QT-prolongation heart rhythm disturbances; it has been in use for decades.
  • Rationale offered early in the pandemic: a possible mechanism of action, in vitro activity against SARS-CoV-2, and a few early observational/non-randomised studies suggesting efficacy, combined with a “desperate need for something.”
  • Step 1 applied: the clinical questions were framed as: does hydroxychloroquine improve outcomes in COVID-19, does it prevent transmission, and if benefits exist do they outweigh harms? The gold-standard design to answer these is a randomised controlled trial.
  • What happened despite insufficient evidence: promotion by some clinicians/scientists and global political leaders (including a tweet from Donald Trump), heavy media coverage, and FDA emergency-use authorisation, leading to large increases in prescribing and online purchasing and global shortages of hydroxychloroquine/chloroquine. In Aotearoa/NZ new prescriptions rose four- to five-fold in March 2020 (seven-fold in the USA); prescribing restrictions introduced in late March 2020 returned NZ prescribing to normal.
  • Harms of acting on insufficient evidence: many people were exposed to treatment harms with little evidence of benefit; the drug became difficult to obtain for people who needed it for its established indications (malaria, lupus, rheumatoid arthritis); and there was a risk of false reassurance distracting from more effective pandemic responses.
  • The randomised controlled trial (Boulware et al, NEJM 2020): 821 participants (mostly healthcare workers) in the USA/Canada with recent high-risk COVID-19 exposure, randomised to a five-day course of hydroxychloroquine or placebo within four days of exposure. Primary outcome: laboratory-confirmed or illness-compatible COVID-19 within 14 days. Result: no significant difference in risk of developing COVID-19 between groups, and more side effects in the hydroxychloroquine group.
  • Systematic review (Cochrane, Singh et al, 2021): evaluated chloroquine/hydroxychloroquine for treating COVID-19, for preventing infection in at-risk people, and for preventing infection after exposure, including RCTs, searched up to 15 September 2020.
    • Treatment: 12 trials, 8569 participants; little or no effect on risk of death, probably no effect on progression to mechanical ventilation; adverse effects tripled versus placebo.
    • Prevention: no trials yet for pre-exposure prevention; two trials for post-exposure prevention, neither showing benefit; unlikely to be effective for prevention.

Take-home: decisions should be "guided by an evidence base that comes from high-quality research, not from rushed judgements based on preliminary studies, perspectives from individual scientists, or pressure from political leaders" (Englund et al, 2020).

EBP across your training

  • EBP is relevant across medicine: establishing efficacy of treatments/vaccines, choosing surgical procedures, assessing screening/preventive programmes, and answering patients’ questions about treatment options, among others.
  • Bruner’s “spiral curriculum” model: content recurs at increasing difficulty/mastery across training rather than being taught once. For EBP this sequence is POPH192, then ELM2 EBP (current point), then ELM3 EBP, then ALM EBP within GP/medicine/surgery placements, then vocational training, then the rest of one’s career.
  • ELM2 EBP lecture sequence: introduction to EBP; overview of study design; observational studies in clinical medicine; principles of test characteristics and clinical reasoning; what doctors need to know about RCTs; what doctors need to know about systematic reviews and meta-analyses; plus three tutorials, and assessment by critical appraisal of a paper (given a week in advance).
  • ELM3 EBP: an overview using a contemporary clinical question, and identifying what information is needed to answer it.

Self-test

  1. Define evidence-based medicine (EBM).
  2. Describe the three elements whose overlap defines evidence-based practice in the clinical decision-making Venn diagram.
  3. Explain why patient dignity is described as relevant to evidence-based practice, not just the evidence itself.
  4. List four consequences of practising without good evidence.
  5. Distinguish the type of study best suited to answering “what causes the disease?” from the type best suited to “how common is the disease?”
  6. List the levels of the hierarchy of scientific evidence from lowest to highest.
  7. Give three examples of sources that are not considered scientific evidence.
  8. Describe the five steps of evidence-based practice in order.
  9. In the hydroxychloroquine COVID-19 case, what was the initial rationale for its use, and what did the subsequent RCT (Boulware et al) find?
  10. According to the Cochrane review, what were the findings on hydroxychloroquine for (a) treating COVID-19 and (b) preventing it?
  11. Distinguish the OCEBM levels of evidence used to answer a treatment-benefit question from those used to answer a treatment-harms question.
  12. Using the hydroxychloroquine example, explain how acting before high-level evidence was available caused harm, and identify what should have been done differently according to evidence-based practice principles.

Answers

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