BECOMING AN BECOMING AN INFORMATION INFORMATION MASTER-or- MASTER-or-

How to feel good about not How to feel good about not knowing everythingknowing everything

AGENDAAGENDA• Context and some philosophyContext and some philosophy• Learn what is: ‘patient-oriented’ evidence Learn what is: ‘patient-oriented’ evidence • Asking clinical questionsAsking clinical questions• Look at a couple examples from therapy articlesLook at a couple examples from therapy articles• Learn to calculate some thingsLearn to calculate some things• Practice calculating some thingsPractice calculating some things• Learn what the numbers mean for practiceLearn what the numbers mean for practice• If timeIf time, some searching, some searching

EVIDENCE BASED EVIDENCE BASED MEDICINEMEDICINE

The judicious and conscientious use The judicious and conscientious use of current best evidence from of current best evidence from medical care research in making medical care research in making decision about the care of decision about the care of individuals. individuals.

DEFINITION FOR THE 21DEFINITION FOR THE 21STST CENTURYCENTURY

• a set of tools and resources for finding a set of tools and resources for finding and applying current best evidence and applying current best evidence from research for the care of individual from research for the care of individual patients. patients.

• ““evidence based medicine seeks to evidence based medicine seeks to empower clinicians so that they can empower clinicians so that they can develop independent views regarding develop independent views regarding medical claims and controversies”medical claims and controversies”

The ProblemThe Problem

• ““In family medicine it was recently In family medicine it was recently estimated that a physician would estimated that a physician would need to spend 627.5 hours just to need to spend 627.5 hours just to read the 7287 articles relevant to read the 7287 articles relevant to primary care published each month”primary care published each month”

Clinical expertise

Patient’s preferences

ResearchEvidence

HOW DO WE MAKE CLINICAL DECISIONS?

The bigger pictureThe bigger picture

• More health care does NOT equal more More health care does NOT equal more healthhealth

• Diminishing returns on health care Diminishing returns on health care spending beyond $1000/capita/yearspending beyond $1000/capita/year

• How much does Canada spend?How much does Canada spend?• How likely is a BP patient in family How likely is a BP patient in family

medicine to be on a thiazide diuretic ($) medicine to be on a thiazide diuretic ($) compared to ACE-I in a specialist setting compared to ACE-I in a specialist setting ($$$)?($$$)?

APPLICATION OF EBM APPLICATION OF EBM TO PRIMARY CARETO PRIMARY CARE

• Review of the literature on patient Review of the literature on patient centered care:centered care:– Patient satisfaction is the highest when Patient satisfaction is the highest when

they take part fully in decision makingthey take part fully in decision making– Patient compliance with the strategy is Patient compliance with the strategy is

better when the decision has been better when the decision has been made in partnershipmade in partnership

APPLICATION OF EBM APPLICATION OF EBM TO PRIMARY CARETO PRIMARY CARE

Clinical Expertise (I.e. Parachute prevents death!!)

There will never be an RCT to prove that Pap screening reduced cervical cancer or that cigarette smoking causes lung cancer

Patient-oriented Patient-oriented evidence?evidence?

Anti-depressants may benefit some patients with inflammatory bowel diseaseby Suzanne MorrisonMay 02, 2008

VS

Acarbose in the prevention of cardiovascular disease and hypertension in patients with impaired glucose tolerance

THE WELL BUILT THE WELL BUILT CLINICAL QUESTIONCLINICAL QUESTION

• Anatomy of a question: Anatomy of a question: PICOPICO

PP- What is the type of - What is the type of patientpatient or or problemproblem

to be addressedto be addressed

I-I- What is the What is the interventionintervention or exposure or exposure being considered?being considered?

CC- What is the - What is the comparisoncomparison intervention intervention or exposure (if relevant)or exposure (if relevant)

O-O- What are the What are the clinical outcomesclinical outcomes of of interestinterest

Acarbose in the prevention of cardiovascular disease and hypertension in patients with impaired glucose tolerance

Level of evidence = AAcarbose is effective in the prevention of cardiovascular events and hypertension in patients with impaired glucose tolerance.In an international, multicentre trial 1, 1429 patients with a mean age of 54.5 years and BMI 30.9 were randomized to receive either acarbose 100 mg 3 times a day or placebo. Decreasing prostprandial hyperglycemia with acarbose was associated with a 2.5% absolute risk reduction and a 49% relative risk reduction in the development of cardiovascular events (HR 0.51, 95% CI 0.28 to 0.95), and a 5.3% absolute risk reduction and 34% relative risk reduction in the incidence of new cases of hypertension (HR 0.66, 95% CI 0.49 to 0.89). The risk reduction was no influenced by adjusting for major risk factors.References

1.Chiasson JL, Josse RG, Gomis R, Karasik A, Laakso M, for the STOP-NIDDM Trial Research Group. Acarbose treatment and the risk of cardiovascular disease and hypertension in patients with impaired glucose tolerance. JAMA 2003;290:486-494

Example of a POEM (CMA)

Consider a study in which 15% (0.15) of the control group and 10% (0.10) of the treatment group died after 2 years of treatment. The results can be expressed in many ways as shown below.

What did those numbers mean What did those numbers mean in practice?in practice?

Measure Meaning ExampleRelative risk (RR)

• risk of outcome in the treatment group divided by the risk of outcome in the control group

RR how many times more likely it is that an event will occur in the treatment group relative to the control group.RR = 1 •no difference between the 2 groupsRR < 1 •treatment reduced the risk of the outcomeRR > 1 •treatment increased the risk of the outcome

RR = 0.1/0.15 = 0.67

Since RR < 1, the treatment decreases the risk of death

Measure Meaning ExampleAbsolute risk reduction (ARR)

• risk of outcome in the control group minus risk of outcome in the treatment group (also known as the absolute risk difference)

ARR tells us the absolute difference in the rates of events between the two groups and gives an indication of the baseline risk and treatment effect.ARR = 0 means that there is no difference between the 2 groups (thus, the treatment had no effect)

ARR = 0.15-0.10

= 0.05 (5%)

•The absolute benefit of treatment is a 5% reduction in the death rate.

Measure Meaning ExampleRelative risk reduction (RRR)

•=ARR divided by the risk of outcome in control group (or, 1 - RR)

RRR tells us the reduction in rate of the outcome in the treatment group relative to the control group. By HOW MUCH did the intervention improve the outcome?

RRR = 0.05/0.15

= 0.33 (33%)

OR

1-0.67 = 0.33 (33%)

Measure Meaning ExampleNumber needed to treat (NNT) = 1/ARR

NNT tells us the number of patients we need to treat with the treatment under consideration in order to prevent 1 bad outcome.

NNT = 1/0.05 = 20

•We would need to treat 20 people for 2 years in order to prevent 1 death.

Let’s do an example on Let’s do an example on the boardthe board

What are the numbers for our example?What are the numbers for our example?

Patients Understand pictures better than RRR, NNT

Knowing how to use your Knowing how to use your time wiselytime wisely

Look at literature similar Look at literature similar to a Drug Repto a Drug Rep

• Pharmaceutical "reps" are now much more informative than they used to be, but they may show ignorance of basic epidemiology and clinical trial design

• The value of a drug should be expressed in terms of safety, tolerability, efficacy, and price

• The efficacy of a drug should ideally be measured in terms of clinical end points that are relevant to patients; if surrogate end points are used they should be valid

• Promotional literature of low scientific validity (such as uncontrolled before and after trials) should not be allowed to influence practice

• identify, for this patient, the ultimate objective of treatment (cure, prevention of recurrence, limitation of functional disability, prevention of later complications, reassurance, palliation,

relief of symptoms, etc);

• select the most appropriate treatment, using all available evidence (this includes considering whether the patient needs to take

any drug at all); and

• specify the treatment target (to know when to stop treatment, change its intensity, or switch to some other treatment).

E.g. hypertensionE.g. hypertension

• the ultimate objective of treatment is to prevent (further) target organ damage to brain, eye, heart, kidney, etc (and thereby prevent death);

• the choice of specific treatment is between the various classes of antihypertensive drug selected on the basis of randomised, placebo controlled and comitemtive trials—as well as non-drug treatments such as salt restriction; and

• the treatment target might be a phase V diastolic blood pressure (right arm, sitting) of less than 90 mm Hg, or as close to that as tolerable in the face of drug side effects.

Good surrogate endpointGood surrogate endpoint• The surrogate end point should be reliable, reproducible,

clinically available, easily quantifiable, affordable, and show a "dose-response" effect (the higher the level of the surrogate end point, the greater the probability of disease)

• It should be a true predictor of disease (or risk of disease). The relation between the surrogate end point and the disease should have a biologically plausible explanation

• It should be sensitive—a "positive" result in the surrogate end point should pick up all or most patients at increased risk of adverse outcome

• It should be specific—a "negative" result should exclude all or most of those without increased risk of adverse outcome

• There should be a precise cut off between normal and abnormal values

• It should have an acceptable positive predictive value—a "positive" result should indicate a high likelihood of the outcome

Database searching for Database searching for evidenceevidence

• Pubmed clinical queries (single articles, Pubmed clinical queries (single articles, specific)specific)

• Health Knowledge Central (general site Health Knowledge Central (general site compiling other resources)compiling other resources)

• Cochrane database (high quality for Cochrane database (high quality for therapy but not many topics)therapy but not many topics)

• Bandolier (critically appraised for you)Bandolier (critically appraised for you)• E-medicineE-medicine• Up to dateUp to date

Search questions?Search questions?

• Treatment of subclinical hypothyroidism?• 42 year old patient with sudden onset of

severe hypertension refractory to treatment. - Who should be screened for secondary causes of hypertension?

• 60 year old woman with ‘squeezing’ chest pain, controlled hypertension- is an ECG useful to determine need to go to ER?