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Journal Club

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by

Andrew Miesner

on 26 September 2016

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Transcript of Journal Club

Journal Club
ENHANCE TRIAL
Power
Did they provide a power calculation?

Did they recruit and analyze the proper amount of patients?

Is this a problem?
Outcomes
Surrogate Outcomes versus "Hard" Outcomes
Represents what you are really trying to study
examples:
Blood Pressure
versus
Stroke
LDL
versus
Heart Attack
INR
versus
Bleeds
Scales
versus
events
May or may not hold clinical significance or validation

Composite Outcomes
Multiple events counted towards a common outcome
"
Death
or
Non-fatal MI
or
Need for Revascularization
"
Very difficult to report or interpret into clinical practice

WHY?
Reporting Outcomes from Trials...
Primary outcomes versus secondary outcomes
Remember what the study was actually designed for
Secondary outcomes are good hypothesis generators
Practice with NNT and NNH : SHARP Trial (2011)
NNT
PHAR110 - Topics in Internal Medicine
Andrew Miesner, PharmD, BCPS
Associate Professor of Pharmacy Practice
Drake University College of Pharmacy & Health Sciences
Objectives
• Describe the background, methods, and results of a journal article.

• Describe the outcomes of a study in terms of its primary and secondary endpoints and their statistical and clinical significance.

• Compare and contrast the outcomes and methods of a trial with that of “real world” circumstances.

• Calculate a number needed to treat (NNT) and/or number needed to harm (NNH).

• Discuss methodical strengths and weaknesses of a given article.

• Compare and contrast the conclusions of authors with that of your own from a given article.

• Kastelein JP, et al. Simvastatin with or without ezetimibe in familial hypercholesterolemia. N Engl J Med 2008;358:1431-43.
Power = 1 - Beta
Beta = The probability of making a type II error
Type II Error = Saying there is no difference when one actually exists
Type I Error = Saying there is a difference when there really isn't one
Power is the strength of your microscope
If you failed to reject the null hypothesis... it's a very big problem.
If you found a statistical difference... it's a small problem.
How do you fix the problem?
Increase the sample size
Power calculations should be done
a-priori
More People = Power!
Do a meta-analysis
"Fatal Flaw"
There would have likely always been a difference, but the measurement is now less precise.
Clinically versus Statistically significant

P-value is modestly helpful (...and sometimes not reported)
Confidence interval and OR/HR interpretation

IMPROVE-IT Trial (2015)...
Major coronary event reduction:
HR 0.936 (95% CI, 0.89 to 0.99)
, P = 0.016

Any Stroke:
HR 0.86 (95% CI, 0.73 to 1.00)
, P = 0.05

Hemorrhagic Stroke:
HR 1.38 (95% CI, 0.93 to 2.04)
, P = 0.11
Absolute versus Relative Risk

SHARP Trial (2011)
A drug rep tells you that Vytorin decreased CV events by 16% in CKD patients over 4 years versus simvastatin alone. It was "very statistically significant with a p-value of 0.0021." You ask to see the study and turn to the primary outcomes.

Vytorin CVEs  526 / 4650 (11.3%)
Simvastatin CVEs  619 / 4620 (13.4%)
Difference  93 less events

Number needed to treat and number needed to harm should only be conducted on statistically significant outcomes and should also report a population and time frame of treatment.
Relative Risk Reduction

treatment events / treatment group
1 - -------------------------------------
placebo events / placebo group
( )
0.113
1 - ------ = 0.157 or ~16%
0.134
( )
Absolute Risk Reduction takes into account the control (baseline) risk.

So what?
Vytorin CVEs  526 / 4650 (11.3%)
Simvastatin CVEs  619 / 4620 (13.4%)
Difference  93 less events

1 1
NNT = ------------------------ = ---------------------------
Absolute risk reduction Treatment - placebo rate
Dr. Oz wants to sell you "Magic Beans."
He is a trustworthy surgeon and tells you that they reduce the risk of diabetes by 50%!


*Actual Rates with "Magic Beans" = 0.5% versus 1% with placebo
1 1
NNT = ---------------- = --------- = ~48 people with CKD treated for
0.134 - 0.113 0.021 four years to prevent one event
NNH
1 1
NNH = ------------------------ = ---------------------------
Absolute risk of ADR Treatment - placebo rate
You notice that the incidence of colon cancer was slightly higher in the Vytorin-treated group.

Vytorin  53/4818 (1.1%)
Simvastatin  35/4375 (0.8%)
Difference  18 less events

1 1
NNH = ---------------- = --------- = ~334 people with CKD treated for
0.011 - 0.008 0.003 four years to develop cancer
LEADER Trial Results
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