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TEMPLATES FOR CONTRIBUTORS TO THE CD FOR THE 2ND EDITION OF EBM

Many thanks for agreeing to contribute to the CD that will accompany the 2nd edition of the EBM book. Not only do we think that your contribution will make the book generally more useful for folks in your discipline; we think it also gives you a specific, golden opportunity to tell them how you see evidence-based practice impinging on your discipline and to point them to the most useful e-b resources.

Moreover, you might want to use this opportunity to test out ideas that you’re developing for the eventual inclusion in a book or manual (such as the manuals several of you are developing in collaboration with Sharon Straus). Because we (not the publisher) hold all the rights to the CD, putting your ideas in it won’t restrict you in any way from expanding on them elsewhere.

To give you a better idea of what we’d like to receive from you, and help you provide it in an easily-incorporated way, we’re providing this template that you can fill-in with your contribution (its rows will expand to hold as much information as you’d like to submit). If you’d like to see a fuller set of examples, including those from some other disciplines, contact Sharon Straus at straus@home.com

If you have any other questions along the way, please contact either Sharon (address just above) or Dave Sackett at sackett@cebm.jr2.ox.ac.uk

Cheers

GENERAL INFORMATION:

Your name, title, and affiliation as you’d like it to appear in the final version of things:
 

If you’re willing to have readers contact you, your contact information:
 

The title you’d like us to use for your section (eg, Evidence-Based Surgery)
 

INTRODUCTORY COMMENTS:

Any introductory comments you’d like to use to open your section (special issues in definition, or the need for making your discipline more evidence-based, etc)
 

SPECIAL RESOURCES:

Any special books, journals, articles, websites, etc that members of your discipline might wish to follow-up (include especially any articles or books you have written/ are writing):
 

PACKAGES:

The key portion of your contribution is a set of packages describing and solving specific questions about the diagnosis, prognosis, therapy, and causes of some typical health conditions and problems faced by members of your discipline.

Each package consists of:

  1. A brief clinical scenario describing the patient whose problem starts the whole process.
  2. The 3-part question (the patient/ the manoeuver/ the outcome of interest) that arises from the patient’s problem [the "clinical questions" chapter from the 1st edition is attached in case you haven’t seen it.].
  3. The searching strategy that yielded a useful article for answering the question.
  4. A critical appraisal of that article, using a standard format and ending in how you would apply its results to your unique patient and their values and expectations.
  5. A "CAT" that summarises the critical appraisal (we’ll mail you a CATMaker; if you want a headstart, you can get a copy with nine lives (CATNipper) from our website at: http://www.cebm.net/docs/catmaker.html)

To give you a better idea of what we have in mind, here’s an example:

SAMPLE Clinical Scenario:

You see a 72 year old man referred to you by his GP with sudden onset of left sided weakness and numbness, and a left homonymous hemianopia. His past medical history is unremarkable and he is not on any medications. On physical exam he has improved but still has evidence of moderate left-sided weakness consistent with MCA territory stroke; he also has a right carotid bruit suggesting that he might have high-grade stenosis. His GP had told him about an operation that could "clean" his arteries out and wanted to know if this could be done. You aren’t sure.

SAMPLE 3-part question:

In patients with a recent cerebrovascular event and high-grade stenosis of the ipsilateral internal carotid artery, does carotid endarterectomy reduce the risk of subsequent major stroke and death?

SAMPLE Searching terms and evidence source:

You start up Best Evidence, enter "carotid endarterectomy," and you find the abstract for the randomised trial of endarterectomy in patients with symptomatic high-grade stenosis from the New England Journal report of the North American Symptomatic Carotid Endarterectomy Trial. The abstract and commentary look very promising, so you go to the library and copy the original article: (N Engl J Med 1991;325:445-53).

SAMPLE COMPLETED THERAPY WORKSHEET: page 1 of 2

Citation: North American Symptomatic Carotid Endarterectomy Trial Collaborators: Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. New England Journal of Medicine 1991; 325: 445-53

Are the results of this single preventive or therapeutic trial valid?

Was the assignment of patients to treatments randomised?

-and was the randomisation list concealed?

 

Yes

Yes

Were all patients who entered the trial accounted for at its conclusion? -and were they analysed in the groups to which they were randomised?

 

Yes

Yes

Were patients and clinicians kept "blind"

to which treatment was being received?

 

No, but events went to "blinded" adjudicators who decided whether and how severe a stroke had occurred.

Aside from the experimental treatment,

Were the groups treated equally?

 

Yes, with "best medical Rx" including aspirin and vigorous antihypertensive therapy.

Were the groups similar at the start of the trial?

 

Yes

Are the valid results of this randomised trial important?

YOUR CALCULATIONS:

MAJOR STROKE

OR DEATH

Relative Risk Reduction

RRR

Absolute Risk Reduction

ARR

Number Needed to Treat

NNT

CER

EER

CER - EER

CER

CER - EER

1/ARR

.181

 

.080

56%

(28% TO 84%)

.101

(.050 TO .152)

10

(7 to 20)

95% Confidence Interval (CI) on an NNT = 1 / (limits on the CI of its ARR) =

95% CI = +/- 1.96 * sqrt((CER*(1-CER)/no. of control pts) + (EER*(1-EER)/no. of exp. pts.)) = +/- 1.96 * sqrt((0.181*(1-0.181)/331) + (0.080*(1-0.080)/328))

SAMPLE THERAPY WORKSHEET: page 2 of 2

Can you apply this valid, important evidence about therapy in caring for your patient?

Do these results apply to your patient?

  

Is your patient so different from those in the trial that its results can’t help you?

 

Similar

How great would the potential benefit of therapy actually be for your individual patient?

 

 		 

Method I: f

 

Risk of the outcome in your patient, relative to patients in the trial. Expressed as a decimal: 1

NNT/F = _10__/__1__ = ____10___

(NNT for patients like yours)

Method II: 1 / (PEER x RRR)

Your patient’s expected event rate if they received the control treatment: PEER:______

1 / (PEER x RRR) = 1/________ = _______

(NNT for patients like yours)

Are your patient’s values and preferences consequences?

Satisfied by the regimen and its

Do your patient and you have a clear assessment of their values and preferences?

 

Needs to be addressed in each patient

Are they met by this regimen and its consequences?

 

Needs to be addressed in each patient

Additional Notes:

  1. Need to know the perioperative stroke rate for my surgeon.
  2. Need to know the accuracy of carotid ultrasound at my hospital.
  3. See also the European Carotid Surgery Trial (Lancet 1991;337:1235-43)

SAMPLE CAT

Carotid endarterectomy reduces stroke and death in symptomatic pts with high grade stenosis (NASCET).

Clinical Bottom Line:

In pts with recent hemispheric or retinal TIAs or nondisabling strokes, who have 70-99% stenosis of ipsilateral ICA, carotid endarterectomy decreases the risk of all stroke (NNT=7), major or fatal stroke (NNT=11), and major stroke or death (NNT=10) at 2 yrs.
 

The Patient:

72 yr old man with left sided weakness, past medical history unremarkable

Three-part Question:

In patients with a recent cerebrovascular event, does carotid endarterectomy reduce the risk of subsequent major stroke and death?

Search Terms:

carotid endarterectomy in Best Evidence

Appraised by: Sharon Straus & Dave Sackett; Sept 26, 1996

The Study:

  1. Pts <80 yrs old, hemispheric TIA or monocular blindness <24 hrs or nondisabling stroke within previous 120 days in association with stenosis of 30-99% in ipsilateral ICA who were stratified into 2 strata - 30-69% and 70-99% stenosis.
  2. Control group: (N=331) Medical care consisted of ASA (1300 mgs unless side effects), treatment of hypertension, hyperlipidemia or diabetes if appropriate. Follow up at 1,3,6,9,12 months and then q 4 months thereafter.
  3. Experimental group: (N=328) Medical care and carotid endarterectomy. Follow up as with control group.

The Evidence:

Outcome

Time to Outcome

RRR

95% CI

ARR

95% CI

NNT

95% CI

any stroke

2 yrs

54%

33% to 76%

0.150

0.090 to 0.210

7

5 to 11

major or fatal stroke

2 yrs

72%

40% to 100%

0.094

0.052 to 0.136

11

7 to 19

any major stroke or death

2 yrs

56%

28% to 84%

0.101

0.050 to 0.152

10

7 to 20

Comments:

1. trial stopped early in pts with high grade stenosis because of evidence of efficacy of surgery

2. no patient lost to follow up and no pt withdrawn

3. extrapolation to your hospital - if your hospital’s perioperative risk of major stroke and death exceeds 2.1%, benefit of surgery starts to fall and if the rate of major complications approaches 10% the benefit vanishes entirely.

Expiry date: 1998

References:

NASCET Collaborators: Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med 1991;325:445-53

THERE ENDETH THE SAMPLE, AND HERE YOU TAKETH OVER!

GOOD LUCK!

CONTACT SHARON STRAUS OR DAVE SACKETT WITH ANY QUESTIONS.

THANKS FOR YOUR CONTRIBUTION!

DIAGNOSIS

Clinical Scenario:
 

3-part question:
 

Searching terms and evidence source:
 

DIAGNOSIS WORKSHEET: page 1 of 2

Citation:

Are the results of this diagnostic study valid?
  1. Was there an independent, blind comparison with a reference ("gold") standard of diagnosis?
  
  • Was the diagnostic test evaluated in an appropriate spectrum of patients (like those in whom it would be used in practice)?
    		•   
  • Was the reference standard applied regardless of the diagnostic test result?

    •  

    		  

    Are the valid results of this diagnostic study important?

    SAMPLE CALCULATIONS (see p 120 of the EBM book):
       

    Target Disorder

    (iron deficiency anaemia)

    Totals
       

    Present

    Absent

    		  

    Diagnostic

    Test Result

    Positive

    (<65 mmol/L)

    731

    a

    270

    b

    a+b 1001

    (serum ferritin)

    Negative

    (>65 mmol/L)

    78 c

    d 1500

    c+d 1578
     

    Totals

    809 a+c

    b+d 1770

    a+b+c+d 2579

    Sensitivity = a/(a+c) = 731/809 = 90% Specificity = d/(b+d) = 1500/1770 = 85%

    Likelihood Ratio for a positive test result = LR+=sens/(1-spec)=90%/15%=6

    Likelihood Ratio for a negative test result=LR-=(1-sens)/spec=10%/85%=0.12

    Positive Predictive Value = a/(a+b) = 731/1001 = 73%

    Negative Predictive Value = d/(c+d) = 1500/1578 = 95%

    Pre-test Probability (prevalence) = (a+c)/(a+b+c+d) = 809/2579 = 32%

    Pre-test-odds = prevalence/(1-prevalence) = 31%/69% = 0.45

    Post-test odds = Pre-test odds x Likelihood Ratio

    Post-test Probability = Post-test odds/(Post-test odds + 1)

    YOUR CALCULATIONS:
       

    Target Disorder

     

    Totals
       

    Present

    Absent

    		  

    Diagnostic

    Test Result

    Positive

     

    a

    B

    a+b
     

    Negative

     

    c

    D

    c+d
     

    Totals

    a+c

    b+d 1770

    a+b+c+d

    Sensitivity = a/(a+c) = Specificity = d/(b+d) =

    Likelihood Ratio for a positive test result = LR+=sens/(1-spec)=

    Likelihood Ratio for a negative test result=LR-=(1-sens)/spec=

    Positive Predictive Value = a/(a+b) = Negative Predictive Value = d/(c+d) =

    Pre-test Probability (prevalence) = (a+c)/(a+b+c+d) =

    Pre-test-odds = prevalence/(1-prevalence) =

    Post-test odds = Pre-test odds x Likelihood Ratio =

    Post-test Probability = Post-test odds/(Post-test odds + 1) =

    DIAGNOSIS WORKSHEET: page 2 of 2

    Can you apply this valid, important evidence about a diagnostic test in caring for your patient?

    Is the diagnostic test available, affordable, accurate, and precise in your setting?

     

    		  

    Can you generate a clinically sensible estimate of your patient’s pre-test probability (from practice data, from personal experience, from the report itself, or from clinical speculation)

     

    		  

    Will the resulting post-test probabilities affect your management and help your patient? (Could it move you across a test-treatment threshold?; Would your patient be a willing partner in carrying it out?)

    		  

    Would the consequences of the test help your patient?

     

    		  

    Additional Notes:

    NOW PLEASE COMPLETE A DIAGNOSTIC CAT FOR THE ARTICLE YOU FOUND

    (REMEMBER, YOU CAN GET A CATNipper AT http://www.cebm.net/docs/catmaker.html)

    CAT –Title

    Clinical Bottom Line

    Citation

    Clinical Question

    Search terms

    The Study

    The Evidence

    Comments

    Appraiser and Expiry Date

    PROGNOSIS

    Clinical Scenario:
     

    3-part question:
     

    Searching terms and evidence source:
     

    PROGNOSIS WORKSHEET: Page 1 of 2

    Citation:

    Are the results of this prognosis study valid?
    1. Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?

      2.  

    		  
  • Was patient follow-up sufficiently long and complete?

    •  

    		  
  • Were objective outcome criteria applied in a "blind" fashion?

    •  

    		  
  • If subgroups with different prognoses are identified, was there adjustment for important prognostic factors?

    •  

    		  
  • Was there validation in an independent group ("test-set") of patients?

    •  

    		  

    PROGNOSIS WORKSHEET: Page 2 of 2

    Are the valid results of this prognosis study important?

     
    1. How likely are the outcomes over time?

      2.  

    		  
  • How precise are the prognostic estimates?

    •  

    		  

    If you want to calculate a Confidence Interval around the measure of Prognosis: (see Appendix 1 in the EBM book)

    Clinical Measure

    Standard Error (SE)

    Typical calculation of CI

    Proportion (as in the rate of some prognostic event, etc.) where:

    the number of patients = n

    the proportion of these patients who experience the event = p

     

    Ö {p x (1-p) / n}

    where p is proportion and n is number of patients

     

    If p = 24/60 = 0.4 (or 40%) & n=60

    SE=Ö {0.4 x (1-0.4) / 60} = 0.063 (or 6.3%)

    95% CI is 40% +/- 1.96 x 6.3% or 27.6% to 52.4%

    n from your evidence: ________

    p from your evidence: ________

     

    Ö {p x (1-p) / n}

    where p is proportion and n is number of patients

     

    Your calculation:

    SE: ____________

    95% CI:

    Can you apply this valid, important evidence about prognosis in caring for your patient?

     
    1. Were the study patients similar to your own?

      2.  

    		  
  • Will this evidence make a clinically important impact on your conclusions about what to offer or tell your patient?
    		•  

    Additional Notes:

    AND PLEASE COMPLETE A CAT FOR THE PROGNOSIS ARTICLE YOU FOUND

    (REMEMBER, YOU CAN GET A CATNipper AT http://www.cebm.net/docs/catmaker.html)

    CAT – title

    Clinical bottom line

    Citation

    Clinical question

    Search terms

    The study

    The evidence

    Comments

    Appraiser, expiry date

    THERAPY

    Clinical Scenario:
     

    3-part question:
     

    Searching terms and evidence source:
     

    THERAPY WORKSHEET: page 1 of 2

    Citation:

    Are the results of this single preventive or therapeutic trial valid?

    Was the assignment of patients to treatments randomised?

    -and was the randomisation list concealed?

    		  

    Were all patients who entered the trial accounted for at its conclusion? -and were they analysed in the groups to which they were randomised?

    		  

    Were patients and clinicians kept "blind"

    to which treatment was being received?

     

    		  

    Aside from the experimental treatment,

    were the groups treated equally?

     

    		  

    Were the groups similar at the start of the trial?

     

    		  

    Are the valid results of this randomised trial important?

    SAMPLE CALCULATIONS (see pages 134-140 of the EBM book):

    Occurrence of diabetic neuropathy

    Relative Risk Reduction

    RRR

    Absolute Risk Reduction

    ARR

    Number Needed to Treat

    NNT

    Usual Insulin

    Control Event Rate

    CER

    Intensive Insulin

    Experimental Event Rate

    EER

    CER - EER

    CER

    CER – EER

    1/ARR

    9.6%

    2.8%

    9.6% - 2.8% =

    9.6%

    71%

    9.6% - 2.8% = 6.8%

    1/6.8% = 15 pts,

    95% Confidence Interval (CI) on an NNT = 1 / (limits on the CI of its ARR) =

    95% CI = +/- 1.96 * sqrt((CER*(1-CER)/no. of control pts) + (EER*(1-EER)/no. of exp. pts.)) = +/- 1.96 * sqrt((0.096*0.904/730) + (0.028*0.972/711))

    YOUR CALCULATIONS:
     

    Relative Risk Reduction

    RRR

    Absolute Risk Reduction

    ARR

    Number Needed to Treat

    NNT

    CER

    EER

    CER - EER

    CER

    CER – EER

    1/ARR
             

    THERAPY WORKSHEET: page 2 of 2

    Can you apply this valid, important evidence about a treatment in caring for your patient?

    Do these results apply to your patient?

    		  

    Is your patient so different from those in the trial that its results can’t help you?

     

         		 

    How great would the potential benefit of therapy actually be for your individual patient?

     

         		 

    Method I: f

     

    Risk of the outcome in your patient, relative to patients in the trial. expressed as a decimal:_____

    NNT/f = ___/___ =

    (NNT for patients like yours)

    Method II: 1 / (PEER x RRR)

    Your patient’s expected event rate if they received the control treatment: PEER:______

    1 / (PEER x RRR) = 1/________ = _______

    (NNT for patients like yours)

    Are your patient’s values and preferences consequences?

    Satisfied by the regimen and its

    Do your patient and you have a clear assessment of their values and preferences?

     

         		 

    Are they met by this regimen and its consequences?

     

         		 

    Additional Notes:

    AND PLEASE COMPLETE A CAT ON THE THERAPY ARTICLE YOU IDENTIFIED

    (REMEMBER, YOU CAN GET A CATNipper AT http://www.cebm.net/docs/catmaker.html)

    CAT – title

    Clinical bottom line

    Citation

    Clinical Question

    Search terms

    The study

    The evidence

    Comments

    HARM

    Clinical Scenario:
     

    3-part question:
     

    Searching terms and evidence source:
     

    HARM/AETIOLOGY WORKSHEET: Page 1 of 2

    Citation:

    Are the results of this harm study valid?
    1. Were there clearly defined groups of patients, similar in all important ways other than exposure to the treatment or other cause?
    		  
  • Were treatment exposures and clinical outcomes measured the same ways in both groups (e.g., was the assessment of outcomes either objective (e.g., death) or blinded to exposure)?
    		•   
  • Was the follow-up of study patients complete and long enough?

    •  

    		  

    Do the results satisfy some "diagnostic tests for causation"?

         		 
      • Is it clear that the exposure preceded the onset of the outcome?
    		  
      • Is there a dose-response gradient?

     

    		  
      • Is there positive evidence from a "dechallenge-rechallenge" study?
    		  
      • Is the association consistent from study to study?

     

    		  
      • Does the association make biological sense?

     

    		  

    Are the valid results from this harm study important?

       

    Adverse Outcome

    Totals
       

    Present

    (Case)

    Absent

    (Control)

    		  

    Exposed to the

    Yes

    (Cohort)

    a

    b

    a+b

    Treatment

    No

    (Cohort)

    c

    d

    c+d

     
     

    Totals

    a+c

    b+d

    a+b+c+d

    In a randomised trial or cohort study: Relative Risk = RR = [a/(a+b)]/[c/(c+d)]

    In a case-control study: Odds Ratio (or Relative Odds) = OR = ad/bc

    In this study:

    HARM/AETIOLOGY WORKSHEET: Page 2 of 2

    Should these valid, potentially important results of a critical appraisal about a harmful treatment change the treatment of your patient?
    1. Can the study results be extrapolated to your patient?

      2.  

    		  
  • What are your patient’s risks of the adverse outcome?

    • To calculate the NNH for any Odds Ratio (OR) and your Patient’s Expected Event Rate for this adverse event if they were NOT exposed to this treatment (PEER):

    NNH = ___PEER (OR - 1) + 1________

    PEER (OR - 1) x (1 - PEER)

     

    		  
  • What are your patient’s preferences, concerns and expectations from this treatment?

    •  

    		  
  • What alternative treatments are available?

    •  

    		  

    Additional Notes:

    AND PLEASE COMPLETE A CAT FOR THE "HARM" ARTICLE YOU FOUND

    (REMEMBER, YOU CAN GET A CATNipper AT http://www.cebm.net/docs/catmaker.html)

    CAT- title

    Clinical bottom line

    Citation

    Clinical Question

    Search terms

    The study

    The Evidence

    Comments

    Expiry date and appraiser

    SYSTEMATIC REVIEWS

    Clinical Scenario:
     

    3-part question:
     

    Searching terms and evidence source:
     

    SYSTEMATIC REVIEW (of Therapy) WORKSHEET: page 1 of 2

    Citation:

    Are the results of this systematic review (systematic review) of therapy valid?

    Is it a systematic review of randomised trials of the treatment you’re interested in?

     

    		  

    Does it include a methods section that describes:

    		  

    Finding and including all the relevant trials?

     

         		 

    Assessing their individual validity?

     

     

    Were the results consistent from study to study?

     

    		  

    Are the valid results of this systematic review important?

    Translating odds ratios to NNTs. The numbers in the body of the table are the NNTs for the corresponding odds ratios at that particular patient’s expected event rate (PEER).

       

    Odds Ratios (OR)
       

    0.9

    0.85

    0.8

    0.75

    0.7

    0.65

    0.6

    0.55

    0.5
     

    .05

    209

    139

    104

    83

    69

    59

    52

    46

    41
     

    .10

    110

    73

    54

    43

    36

    31

    27

    24

    21

    Control

    .20

    61

    40

    30

    24

    20

    17

    14

    13

    11

    Event

    .30

    46

    30

    22

    18

    14

    12

    10

    9

    8

    Rate

    .40

    40

    26

    19

    15

    12

    10

    9

    8

    7

    (CER)

    .50

    38

    25

    18

    14

    11

    9

    8

    7

    6
     

    .70

    44

    28

    20

    16

    13

    10

    9

    7

    6
     

    .90

    101

    64

    46

    34

    27

    22

    18

    15

    12

    SYSTEMATIC REVIEW (of Therapy) WORKSHEET: page 2 of 2

    Can you apply this valid, important evidence from a systematic review in caring for your patient?

    Do these results apply to your patient?

    		  

    Is your patient so different from those in the systematic review that its results can’t help you?

         		 

    How great would the potential benefit of therapy actually be for your individual patient?

         		 

    Method I: In the table on page 1, find the intersection of the closest odds ratio from the overview and the CER that is closest to your patient’s expected event rate if they received the control treatment (PEER):

         		 

    Method II: To calculate the NNT for any OR and PEER:

    ___1 - {PEER x (1 - OR)}____

    NNT = (1 - PEER) x PEER x (1 - OR)

    		  

    Are your patient’s values and preferences satisfied by the regimen and its consequences?

    Do your patient and you have a clear assessment of their values and preferences?

     

         		 

    Are they met by this regimen and its consequences?

     

         		 

    Should you believe apparent qualitative differences in the efficacy of therapy in some subgroups of patients? Only if you can say "yes" to all of the following:
    1. Do they really make biologic and clinical sense?
  • Is the qualitative difference both clinically (beneficial for some but useless or harmful for others) and statistically significant?
    		•
  • Was this difference hypothesised before the study began (rather than the product of dredging the data), and has it been confirmed in other, independent studies?
    		•
  • Was this one of just a few subgroup analyses carried out in this study?

    • Additional Notes:

    AND PLEASE COMPLETE A CAT FOR THE OVERVIEW YOU FOUND

    (REMEMBER, YOU CAN GET A CATNipper AT http://www.cebm.net/docs/catmaker.html)

    CAT – title

    Clinical bottom line

    Citation

    Clinical Question

    Search terms

    The study

    The evidence

    Comments

    Appraiser, expiry date

    That’s it!

    Again, thanks very much for this.

    ****Could you please send it as an email attachment (either word.doc or .rtf) to Dave Sackett at: sackett@cebm.jr2.ox.ac.uk

    If, on reviewing it, you’d like to consider having it appear not only on our CD but also as an independent publication, by all means go right ahead! If you’d like to discuss it as part of our series of EBCP Handbooks, contact Sharon Straus at:sharon.straus@clinical-medicine.oxford.ac.uk