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How to read a Systematic Review: The FAST tool

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How to read a Systematic Review: The FAST tool

Find

Appraise

Synthesise

Transferability

Paul Glasziou

Centre for Evidence Based Medicine

University of Oxford

www.cebm.net

- Some immediate & dramatic effects don’t need RCTs*
- Example:
- Child with nasal foreign body
- Dislodged with Parent Kiss method
- Case series of success 15/19
- Botma J Laryngol Otol 2000

* Glasziou, Chalmers, Rawlins, McCulloch BMJ 2007

- For an acutely ill patient, you do a search
- You find several studies: some show significant results but many others don’t

Forest Plot/Blobbogram: of these 17 studies

- Which is the smallest study?
- Which is the largest study?
- How many are statistically significant?
- Which studies are “large enough”?

Of these 17 studies: of streptokinase for MI

For disease X the usual mortality rate is 0%

What sample size is needed to detect a reduction in mortality?

- 100
- 1,000
- 100,000
- 1,000,000

50 events are needed in the control group:

(For an 80% chance of finding a 50% reduction)

Glasziou P, Doll H. Was the study big enough? Two cafe rules. Evid Based Med. 2006;11(3):69-70.

- There is usually a 12% mortality rate
- You think your treatment will lower mortality by 50%

- What sample size is needed?

- There is usually a 12% mortality rate
- You think your treatment will lower mortality by 50%

- What sample size is needed?
- 12% means
- 12/100 or 24/200 or 48/400
- and 50 per 417

- Control + Treatment Groups = 834 in total

- A Systematic Review is a review of a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review.
- Statistical methods (meta-analysis) may or may not be used to analyze and summarize the results of the included studies.

- Question – What is the PICO?
- Finding
- Did they find most studies?

- Appraisal
- Did they select good ones?

- Synthesis
- What to they all mean?

- Transferability of results

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

Most reviews do not pass minimum criteria

A study of 158 reviews*

- Only 2 met all 10 criteria
- Median was only 1 of 10 criteria met

FAST tool = 4 criteria

* McAlister Annals of Intern Med 1999

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- Population
- Intervention
- Comparison
- Outcome(s)

- Find: what is your search strategy?
- Databases?
- Terms?
- Other methods?

Do yourself then

Get neighbour’s help

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- Check for existing systematic review?
- Good initial search
- Terms (text and MeSH)
- At least 2 Databases: MEDLINE, EMBASE, CINAHL, CCTR, ...

- Plus a Secondary search
- Check references of relevant papers & reviews and
- Find terms (words or MeSH terms) you didn’t use
- Search again! (snowballing)

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- Negative studies less likely to be published than ‘Positive’
- How does this happen?
- Follow-up of 737 studies at Johns Hopkins (Dickersin, JAMA, 1992)
- Positive SUBMITTED more than negative (2.5 times)

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

Simes, J. Clin Oncol, 86, p1529

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

Simes, J. Clin Oncol, 86, p1529

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- All positive studies
- All studies with more than 100 patients
- All studies published in BMJ, Lancet, JAMA or NEJM
- All studies registered studies

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- All trials registered at inception,
- The National Clinical Trials Registry: Cancer Trials
- National Institutes of Health Inventory of Clinical Trials and Studies
- International Registry of Perinatal Trials

- www.controlled-trials.com

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

Did they select only the good quality studies?

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

1. Does the death penalty for miscalculation of an NNT discourage future miscalculation?

2. Should we have the death penalty for miscalculation of NNT?

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

Lord et al, J Pers Soc Psy, 1979, p2098

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

28 reviewers assessed one “study” results randomly positive or negative

(Cog Ther Res, 1977, p161-75)

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- Assessment and selection should be:
Standardized “Objective” OR

Blinded to Results

* assessment of quality blind to study outcome

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

Is the AVERAGE effect similar across studies?

- If NO, then WHY?
- Study methods (RAMbo - biases)
- PICO (Patients, Intervention, …)

- If YES, then 2 questions
- Effect in different individuals?
- Which version of treatment?

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

Are the results similar across studies? 3 tests

- Eyeball” test – do they look they same?
- Test of “Null hypothesis” of no variation (p-value)
- Proportion of variation not due to chance (I2)

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

EBM (quick & dirty)

Steps

Ask Question

Search

Appraise

Apply

Time: 90 seconds

< 20 articles

This patient survives!

Systematic Review

Steps

Ask Question

Search ++++ x 2

Appraise x 2

Synthesize

Apply

Time: 6 months, team

< 2,000 articles

This patient is dead

Find a systematic review!! (and appraise it FAST)

- Advantages
- Larger numbers & power
- Robustness across PICOs

- Disadvantages
- May conclude small biases are real effects

- Question – What is the PICO?
- Finding
- Did they find most studies?

- Appraisal
- Did they select good ones?

- Synthesis
- What to they all mean?

- Transferability of results

Combined results

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- STUDY: meta-analysis of behavioural interventions for insomnia adults
- “.. confirms the efficacy of behavioral interventions for person with chronic insomnia.“

- PROBLEM: No regimens for ‘behavioural intervention’ described
- Author asked: “what specific treatment regime (or regimes) would you recommend based on your review?”
- Author response: “It was found that cognitive, behavioral and relaxation therapies all in general lead to similar improvements in sleep outcomes---although cognitive approaches might have been a bit better. The references for these studies are found in the article. “

Rx

“Behavioural

Intervention”

- Advantages
- Larger numbers & power
- Robustness across PICOs

- Disadvantages
- May conclude small biases are real effects

- What are the overall results?
- Similarity of results
- Heterogeneity statistic

- Similarity of question (PICO)
- Your judgement!

Traditional

Many questions

No search methods

No inclusion criteria

No combining studies

Systematic

One question

Explicit search

Explicit inclusion criteria

Combine study results(meta-analysis)

Which are

(i) statistically significant * and (ii) Clinically significant +?

(a*+)

(b+)

(c*)

(d)

Minimum clinical

Important difference

No difference

- Which studies (presented as Odds Ratio):
- Are not statistically significant?
- Have < 50 patients in the control arm?

For continuous outcomes, number per arm is

17 / (“worthwhile difference” measured in SDs)

In a small randomized double-blind trial of a new treatment for acute myocardial infarction, the mortality in the treated group was half that in the control group, but the difference was not significant. We can conclude that:

- The treatment is useless
- there is no point in continuing to develop the treatment
- the reduction in mortality is so great that we should introduce the treatment immediately
- we should keep adding cases to the trial until the Normal test for comparison of two proportions is significant
- we should carry out a new trial of much greater size

FIND

APPRAISE

SYNTHESISE

TRANSFERABLE

- Are variations in results between studies consistent with chance?
(Test of homogeneity: has low power)

- If NO, then WHY?
- Variation in study methods (RAMbo - biases)
- Variation in PICO (Patients, Intervention, …)

- 10 trials of bed rest after spinal puncture
- no change in headache with bed rest
- Increase in back pain

- Protocols in UK neurology units - 80% still recommend bed rest after LPSerpell M, BMJ 1998;316:1709–10
- …evidence of harm available for 17 years preceding...

*Allen, Glasziou, Del Mar. Lancet, 1999