Evidence-Based Medicine: PICO Format and Search Strategies

PICO and Searching for Evidence

• PICO stands for Population, Intervention, Comparison, and Outcome
• A well-structured, answerable question is crucial in finding evidence

Asking an Answerable Question

• Unanswerable question: What helps with insomnia?
• Structured, answerable question: PICO format
  • P: Population (e.g., Marion, a retired woman who flies frequently)
  • I: Intervention (e.g., wearing elastic stockings)
  • C: Comparison (e.g., not wearing elastic stockings)
  • O: Outcome (e.g., reducing the risk of deep vein thrombosis)

Searching for Evidence

• Databases used to search for evidence: PubMed, EBSCO, CINAHL, MEDLINE, Google Scholar
• PubMed searching:
  • Boolean Operators: AND, OR, NOT (capitals important)
  • Truncation: * (e.g., hyperten* = hypertension, hypertensive)
  • Field descriptions: specify fields to search, e.g., date, author name, journal, title, page number, abstract
  • Advanced search builder: helps to be more specific in your search
  • MeSH Terms: Medical Subject Headings, controlled vocabulary, specify exactly what you're looking for

Pre-synthesized Evidence

• Cochrane Library: HIGHLY rigorous SRs and MAs
• Natural Medicines: access through CCNM library and CAND member website
• Trip Database: free and upgraded version
• Others, subscription: UpToDate, Examine.com

Sourcing Full-Text Articles

• Google Scholar
• Research Gate
• Email the study author: corresponding author, "pre-publication copy"

Practice Exercises

• Does the DASH Diet improve blood pressure in adults? If so, by how much?
• Can eating blueberries protect against the development of Alzheimer's Disease?
• More practice exercises...

Systematic Reviews

• A systematic review in 1987 on corticosteroid treatment in pre-term births showed that a short, inexpensive course of corticosteroid treatment substantially reduced the risk of premature deaths due to complications.

Objectives

• Recognize the important features and strengths of a systematic review or meta-analysis
• Interpret an odds ratio and a forest plot
• Design a search strategy to find a systematic review on a topic

Methodology

• A clear question is essential (consider PICO)
• Search for the right type of studies relevant to the question, with appropriate design (e.g., RCT for interventions)
• Conduct a comprehensive search of databases, reference lists, unpublished studies, and contact experts, including non-English studies
• Use clear eligibility criteria
• Assess individual study quality

Results

• Determine if combining results was appropriate, considering study similarity and potential heterogeneity
• Use tools like Cochrane Q and I2 to assess heterogeneity
• Be cautious of publication bias, attempting to analyze potential bias using individual study data
• Use funnel plots to visualize potential bias, seeking symmetrical distribution

Publication Bias

• Results of a meta-analysis are only valid if capturing the full range of trial results, avoiding negative studies being overlooked
• Analyze individual study data to assess potential publication bias

Cochrane Collection

• The Cochrane Collaboration provides systematic reviews in a rigorous and consistent fashion
• The Cochrane Library is a reputable, non-biased source of reliable, up-to-date overviews of evidence on specific topics

Cochrane Caution

• Cochrane reviews are notoriously conservative in results, often concluding that 'more research is necessary'

Mini Stats Break

• Statistical significance determines if a difference is due to chance or a real difference
• The P-value represents the odds that the difference is due to chance (e.g., ≤ 0.05 is generally considered significant)
• Confidence intervals (CI) provide a range within which the true result is likely to lie (e.g., 95% CI)

Statistical Significance

• P-value and confidence intervals are used to determine statistical significance
• Variables that influence significance include sample size, variation within and between groups