Is it True: Evaluating Medical Reviews

“The review article itself should be the

product of scientific investigation in which

the participants are original investigations

(research) rather than patients”

Usefulness

Work: Low, good source for POEMs Relevance: If title and abstract or article

conclusion hold promise of POEM, continue Validity: Uncertain

Reviews- Three Basic Types

Textbooks

Academic Reviews

“Translation” Journals

Textbooks

Collection of review articles Minimal, if any, supporting evidence Questionable validity, long lag time to publish

• Average 1-2 years

Most useful for retracing, less hunting and foraging

Academic Reviews

Summary: “Broadly paint landscape” Validity uncertain- begin with conclusions and

find supporting references References often inaccurate and out of date **Expertise of author varies inversely with

quality of review- Oxman/Guyatt**• More later

Must confirm POEMs with original research, increasing work

Academic Reviews

Synthesis: Systematic reviews• Meta-analysis or overviews

Answer one or two specific questions Review primary literature with strict criteria Conclusions supported by available evidence Meta-analysis: Achieve power not possible by

single study

Academic Reviews

Excellent source for hunting and foraging

The Cochrane Library - “Database of Systematic Reviews”

Clinical Evidence (BMJ-BMA)

Clinical Inquiries (FPIN)- SORT

AFP EB Reviews- SORT

Dynamed - SORT

Essential Evidence Plus- SORT

Translation Journals

Quick reads for retracing and sporting Low work, but with low validity, may be zero

usefulness Hunting/foraging: Entering jungle on

starless night

Translation Journals

Common POEMs need original data for

verification, greatly increasing work

Watch for “weasel words”, based on DOEs

and anecdotes

• “it seems”, “may be effective”, “so one may assume”, “it appears”, “in my experience”

Weasel Words

Translation Journals

“Buyer Beware: Unsystematic reviews lead to unsystematic conclusions. Readers looking for a shortcut to understanding evidence about health problems and patient care should at least look for reviews by those who have not taken shortcuts”

Determining the usefulness of reviews

Onto the worksheets!

Reviews: Determining Relevance

A. Addressing specific clinical question?

A. Patient-oriented evidence?

B. Common problem?

C. Change your practice?

Reviews: Determining Validity

Answer ALL worksheet questions Stop = “fatal flaw” Notice how hard this is! Average time for a

good systematic review- 2 years!• Much different from your “usual review/CME talk”

Worksheet Qs: Finding the studies

Clearly stated?• Terms appropriate? MESH-linked? None missing?

Comprehensive?• Medline + another

• MEDLINE misses >50% of articles• Cochrane registry is especially good source • Science Citation Index

• Bibliographic review • Unpublished literature

• conference abstracts, personal correspondence with important investigators or pharmaceutical companies

Done by more than one person and compared

Worksheet Qs: Selecting the studies

Inclusion Criteria• Established a priori

• Minimum factors: Population/problem; intervention/comparison; outcomes; study design

• Prefer no language restriction

• Sometimes validity criteria incorporated (random, blinded, appropriate follow-up, gold standard, etc.)

Best if done independently by 2 investigators• Possibly blinded to author/journal/study results

Worksheet Qs:Validity of included studies

Appropriate criteria?• Assurance that criteria specific to type of article employed

(therapy, diagnosis, prognosis, etc)• If therapy: randomization, blinding, concealed allocation,

follow-up Process independent by > 2 authors?

• Surprising differences!• Why blinding may be important:

• 2 sample articles, same study methods• One finds benefit, other does not• “serious flaws” in article without benefit

Worksheet Qs: Validity

Were the included studies valid?• Garbage in = garbage out

• If yes, no problem

• If no, how did authors handle this?• Exclusion/inclusion criteria for quality of study

• Subanalysis with comparison of results

• Need to consider how these flaws affect results/conclusions

Worksheet Qs: Analyzing the data

Homogeneity vs Heterogeneity: just finding the words and an explanation most important

If NOT homogeneous?• Need qualitative explanation. Is it due to chance vs study

design, population, exposure, or outcome?

Worksheet Qs: Analyzing the data

Appropriateness of combining data:• “Vote” count not usually appropriate

• Important to include ‘magnitude’ of the overall effect

• Cannot be done without some common ground- outcome

Publication bias• Small, negative trials less likely to be published

• Examined by funnel plot

• Number needed to change results

From: Cooper & Hedges: The handbook of research synthesis. 1994

Funnel plot examples

From: Cooper & Hedges: The handbook of research synthesis. 1994

Reviews: Major Points Validity traps to avoid

• Assertions based on DOEs -- avoid perpetuating medical gossip

• Unassessed validity -- Personal experience unreliable as a basis for therapeutic interventions

Missing pieces -- **Quality of the review varies inversely with the expertness of the writer**

Failure to identify level of evidence – Look for LOE’s/ SORT

Reviews- Three Basic Types

Highly Controlled ResearchRandomized Controlled TrialsSystematic Reviews

Physiologic ResearchPreliminary Clinical ResearchCase reportsObservational studies

Uncontrolled Observations&

Conjecture

Effect on Patient-Oriented OutcomesSymptomsFunctioningQuality of LifeLifespan

Effect on Disease MarkersDiabetes (microalbuminuria, GFR, photocoagulation rates)Arthritis (ESR, x-rays)Peptic Ulcer (endoscopic ulcers)

Effect on Risk Factors for DiseaseImprovement in markers (blood pressure, HbA1C, cholesterol)

SORTA

Validity of Evidence

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