the metablog

Posts tagged Evidence based medicine.

The 3rd Horseman: Significance & Relevance

Arguably the most important piece of the evidence-based-medicine puzzle is when we ask ourselves:

"Is this evidence significant? – Is this relevant to my patients and my practice?"

When we talk about the 'quality' of a published research work we largely mean what the epidemiologists refer to as 'internal validity' – the extent to which the study's conclusions are actually warranted given the methodology and results. Internal validity looks only at the study design, conduct and interpretation, and takes into account bias and confounders. While important, internal validity is not alone sufficient.

The significance of a piece of evidence to medicine in general, along with it's relevance to our own practice, is referred to as the external validity. I think that for your and my practice this is often what matters most.

Really, external validity just describes how well the results and conclusions can be generalized to situations and people beyond those in the study.

I think of significance as the cumulative generalizability of a piece of evidence for the specialty and for wider medicine, integrated with how well the evidence agrees with what is already known. Relevance describes how applicable the evidence is to my hospital, my practice – and my patients.

It has significance for you, and relevance for me.

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The 2nd Horseman: Quality Evidence

Our understanding of what makes for quality medical research has improved dramatically over the past three decades. We understand that research must be ethical; should be reproducible; free of bias, so that we may make accurate conclusions; and that confounders be minimised and controlled for. We understand that prospective is best, and large blinded randomized trials are king.

We can articulate that a study must be appropriately powered to answer the question we are asking – but also not over-powered so that we waste resources and goodwill, or continue a study after an answer is known.

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The 1st Horseman: Publication Overload

The number of new medical articles published each month is accelerating. PubMed has over 23 million indexed going back to 19661, adding around 500,000 every year – but that's just the articles they index. There are an estimated 50 million scholary articles in total ever written 2, and currently over 28,000 peer-reviewed journals in print, publishing almost 2 million new articles in 2012 – and that's growing by 3% every year.3

If we focus only on MEDLINE® citations (publications indexed with MeSH, Medical Subject Headings) the number of publications each year is increasing exponentially. The graph below shows annual (not cumulative) MEDLINE® citations. The trendline in orange highlights the challenge of staying-up-to-date: annual medical publications is not just increasing, its accelerating.

Publication Overload

source: http://www.nlm.nih.gov/bsd/medline_cit_counts_yr_pub.html

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  1. Wikipedia: PubMed. 

  2. Jinha, Arif E. Article 50 million: an estimate of the number of scholarly articles in existence. Learned Publishing, Volume 23, Number 3, July 2010, pp. 258-263(6). 

  3. The STM report 2012 - An overview of scientific and scholarly journal publishing

The Four Horsemen of the Medical Research Apocalypse

The evidence-based medicine movement started excitedly in the 1990s, filled with much promise and hope. The way we practice medicine has been improved by EBM, along with the health of our patients. However it has not been all smooth sailing, and the challenges to evidence-based medicine are growing not lessening.

While we know more about the human body, critical care, anesthesia, and resuscitation than ever before, it is conversely more difficult to integrate evidence and guide decisions where they matter: for an individual patient.

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Critically appraising the evidence

It’s hard to keep up with the latest evidence. Not only is the sheer volume of newly published papers overwhelming and the variety of topics broad and wide, but then after finding a paper that piques your interest you are still faced with the tricky task of critically assessing the paper's quality and relevance. Metajournal aims to solve many of these problems, but sometimes you need to just sit down and drag that paper over the keel yourself.

One of the most useful tools I have found are checklists provided by the Critical Appraisal Skills Programme, a UK non-profit based in Oxford. CASP runs workshops that educate healthcare workers and others on how to appraised medical evidence — and they share online the great checklists they use during the workshop under a Creative Commons license.

Find → Appraise → Act

They provide a set of eight critical appraisal tools designed to be used when reading research, covering:

  1. Systematic Reviews
  2. Randomised Controlled Trials
  3. Cohort Studies
  4. Case Control Studies
  5. Economic Evaluations
  6. Diagnostic Studies
  7. Qualitative studies
  8. Clinical Prediction Rule

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