Flinders University Library
Search Smart

Evidence Based Medicine (EBM)

This guide is designed to walk you through the Evidence Based Medicine process: the elements of a well-formulated clinical question, types of studies, and the key critical appraisal questions that help determine the validity of evidence.

Medline, PubMed and Scopus search strategies

Clinical scenario
You are a general practitioner working in a primary health care team who frequently sees older patients reporting memory loss and concerned about the onset of dementia. You routinely use the Mini-Mental State Examination (MMSE) screening tool with these patients to evaluate their cognitive function as you know this tool to be sensitive, valid and reliable. Recently you have heard of a tool called the Mini-Cog which is considered quicker to administer and better for patients who or older, less educated, or from culturally and linguistically diverse (CALD) communities. You wish to find out if the Mini-Cog test is as accurate as the MMSE in detecting Alzheimer's disease or dementia.

PICO

  • Population: Older adults with early signs/symptoms of cognitive impairment
  • Intervention: Mini-Cog screening test (index test)
  • Comparison: Mini-Mental State Examination (the reference standard)
  • Outcome: Accurate diagnosis of dementia or Alzheimer's disease

Clinical question

In older adults with early signs of cognitive impairment, is the Mini-Cog test as accurate as the Mini-Mental State Examination in diagnosing dementia or Alzheimer's disease?

Logic Grid

Concept 1: Mini-Cog test Concept 2: Mini-Mental State Examination Concept 3: Dementia
  • Mini-Cog
  • Minicog
  • Mini-Mental State Exam(ination)
  • MMSE
  • Standardised Mini-Mental State Exam(ination)
  • SMMSE
  • Dementia
  • Alzheimer disease
  • Alzheimer's disease

 

Medline search strategy
Using both MeSH terms (where available) and keywords and applying the Medline 'Reviews' and 'Diagnosis' Clinical Queries filters

PubMed Clinical Queries search strategy

Go to Clinical Queries and enter search string: (Mini-cog OR minicog) AND (Mini-mental state exam* OR MMSE OR SMMSE) AND (Alzheimer* OR dementia)

Choose Diagnosis category and Narrow scope for best search specificity and precision.

Important to note:

  • Use brackets to separate strings of synonyms combined with OR from the AND operator
  • Operators AND/OR must be in uppercase in PubMed and PubMed Clinical Queries
  • You can exclude citations already found in Medline by adding NOT Medline[sb] to the end of the search string. This reduces the search set to newly published studies and reviews possibly not yet available in the Medline database. 

E.g. (Mini-cog OR minicog) AND (Mini-mental state exam* OR MMSE OR SMMSE) AND (Alzheimer* OR dementia) NOT Medline[sb]

This finds an additional three clinically relevant studies (left column) and two systematic reviews (middle column).

Scopus search strategy (Will work also in Web of Science)

Mini-cog OR minicog

AND

"Mini-mental state exam*" OR MMSE OR SMMSE

AND

Alzheimer* OR dementia

Important to note:

  • Double quote marks are needed around phrases in Scopus to keep words together
  • Deselect subject areas Physical Sciences, Social Sciences & Humanities, and Life Sciences but keep Health Sciences selected for more precise results.

We found several systematic reviews in the course of our searching such as these below.

To critically appraise these systematic reviews, we need to consider the following:

1. Were the methods used in the review valid?

  • Did it address a clearly focused question in terms of participants, interventions, comparisons, and outcomes (your PICO). Did it have clearly defined eligibility criteria?
  • Did the review include high quality, relevant studies
    • of robust study design (for example, randomised controlled trials)?
    • that addressed relevant questions?
    • selected by more than one independent reviewer?
  • Is it unlikely that the review missed important, relevant studies? 
    • Is the search strategy reproducible?
    • Did the search strategy include synonyms for all concepts?
    • Is the search strategy sufficiently comprehensive? 
  • Did the review include an assessment of the risk of bias of included studies and was this assessment incorporated into the review finding?
    • Is the method for assessing risk of bias reproducible and accurate?
    • Was the risk of bias assessment conducted by more than one independent assessor?
    • Was it incorporated into the review findings?
  • Did the review combine the results from studies and, if so, was it reasonable to do so?
    • Were the results similar from study to study (was an examination fo heterogeneity undertaken)
    • Were reasons for variations in results discussed? 

2. What are the results of the review?

  • What are the overall results of the review? 
  • How precise are the results? 

3. How relevant are the results to me? 

  • Were all important outcomes considered (from the points of view of individuals/patients, policy makers, healthcare professionals, family/carers, the wider community)?
  • Can the results be applied to my patient/s? Consider how well your patient(s) and practice setting compare with the review population.

Appraisal of individual diagnostic test studies

The following individual diagnostic test studies look promising but need to be appraised for their validity.

Important considerations in appraising a diagnostic study:

  1. Was there an independent, blind comparison with a reference ('gold') standard of diagnosis?
  2. Was the diagnostic 'index' test evaluated in an appropriate spectrum of patients, like those you would see in your practice? Was there a clear description of the disease status of the tested population?
  3. Was there sufficient description o f the methods for performing the test?
  4. Did all participants get the diagnostic test and the reference standard? 
  5. Could the results of the index test have been influenced by the results of the reference standard, or vice versa?
  6. Was the test (or cluster of tests) validated in a second, independent group of patients?
  7. Does this evidence demonstrate an important ability of this test to accurately distinguish patients who do and don't have a specific disorder?
    • Requires a consideration of sensitivity, specificity, post-test probabilities, and likelihood ratios

References

Hoffmann T, Bennett S, Del Mar C. Evidence-based practice across the health professions. 2nd ed. Sydney: Churchill Livingstone; 2013. 416 p.

Straus SE, Glasziou P, Richardson WS, Haynes RB. Evidence-based medicine: how to practice and teach it. 4th ed. Edinburgh: Churchill Livingstone Elsevier; 2011. 293 p.