Reporting drugs and treatments Thomas Abraham JMSC 6090.
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Transcript of Reporting drugs and treatments Thomas Abraham JMSC 6090.
Reporting drugs and treatments
Thomas AbrahamJMSC 6090
What we will learn today
How to evaluate and report on studies The difference between absolute and
relative risk reduction Number needed to treat (NNT) A basic way to interpret P values and
CI (confidence intervals)
Nov 1995, results of a new drug trial
6,595 men in the west of Scotland with elevated cholesterol levels participated in trial that lasted 5 years
One group (treatment group) was given a cholesterol lowering drug, pravastatin
Another group (control group) was given a placebo
The results were impressive
For those who took the drug: 31 % reduction of risk from heart
attacks 28 % reduction of risk of death
from coronary heart disease 31 % reduction of risk from heart
attack, or death from heart disease
7.9%
5.5%
Combined risk from heart attacks and death from heart disease
A7.9%
B5.5%
Control group Treatment group
How do you measure the difference between these two groups?
Risk from heart attack and death from heart disease
Absolute and relative risk reduction
Absolute risk reduction looks at the difference between the treatments: A-B =2.4%
Relative risk reduction looks at how much better one treatment is than the other (A-B/ A) x 100=30.37%
AControl group
BTreatment
Group
7.9%
5.5%
Absolute and relative risk
Absolute risk is your risk of getting a particular disease, or condition
Relative risk measures how much your risk is reduced with the new treatment, or procedure, compared with the old.
Relative risk figures tend to look dramatic
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
Death from coronary heart disease
Series1
AControl1.7 %
BTreatment1.2%
Control: 1.7%; treatment 1.2% Absolute risk reduction= Relative risk reduction=
AControl6.5% B
Treatment 4.6%
Non fatal Myocardial Infarction
Absolute Risk Reduction = ?Relative risk Reduction= ?
What were the different outcomes the study measured?
Which outcome was the treatment the most effective in?
Number needed to Treat (NNT)
The number of persons who needed to be treated with a drug, to prevent one person from getting the disease.
Calculated as the inverse of the absolute risk reduction percentage
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
Death from coronary heart disease
Control1.7 %
BTreatment1.2%
A
Absolute Risk Reduction = A-B= .5% . 5% means out of 100 people, .5 death was preventedTo prevent one death: 200 people need to be treated ( 100/ARR%)Time-5 years. Therefore 200 people over 5 years to prevent 1 case
AControl6.5% B
Treatment 4.6%
Non fatal Myocardial Infarction
Absolute Risk Reduction = A-B= 2.9%
Number needed to treat 100 people, 2.9 heart attacks preventedTo prevent one heart attack= 100/ARR%= 100/2.9Over 5 years
Check list When you hear about a new drug
or treatment, check both absolute and relative risk reduction figures.
http://www.bbc.co.uk/news/health-16961112
Ask ( or calculate) number needed to treat
Ask about possible harms Ask about costs
P values and Confidence Intervals ( CI)
P value or probability value= “The probability of obtaining result at least as extreme if the null hypothesis was true”
P < .05 means a less than 95 percent of the time you will get a similar result
P< .01 means a less than 99% percent of the time you would get a similar result
P values of .05 and less are acceptable
According to scientific convention, P<.05 is significant, and P<.01 is highly significant.
Confidence intervals (CI)
The confidence level tells you the range within which a true value will lie. It is generally measured at the 95% level.
For example, 31 ( 17-43) 95% CI would indicate that 95% probability that the real value is between 17 and 43.
http://www.youtube.com/watch?v=lNFuEcy5ekg&feature=related
From last week
When evaluating research findings- Published or not published?- Quality of study: numbers of people or
cases studied, methodology of study- Newsworthiness
Your course work
Three news stories from journal articles
Due Feb 28, March 28 and March 17(you can turn them in earlier if you wish)
Length: 400-500 words Go to Eureka alert, as well as Jama
and BMJ Links to press releases on our course
website Find an article that you think might be
newsworthy and interesting.
Do some background research on the topic.
Go to Pubmed for earlier studies Contact authors of paper, as well as
people in Hong Kong who might have comments.
Give yourself one week for each
Contacting paper authors
Why? Not to “get a quote” To help bring out the significance, or
importance of study To help you understand things you do
not understand Read the paper and do research before
getting in touch, so you do not ask basic questions
What I will look for
Is the story newsworthy? Have you explained the research well? Have you looked at the costs and
benefits (Look at the health news review
website for an idea of what I will be looking for)