Evaluating Information and Presenting Risk

Today’s Class• Fact Sheet Assignment Review• Evaluating Information• Presenting Risk• In-class Activity• This week’s homework

Fact Sheet Assignment

• Well done!– Nice use of headers, bullets, etc to organize content

– Good sources– Appropriate use of plain language

Fact Sheets• Be Mindful

– Avoid clinical language• “sleep disturbances”• “menstruation”

– Provide intro text before a bulleted list• “Symptoms of iron deficiency anemia include the following:”

– Make sure your bullets are consistent• Formatting (bold, hyphens, etc.)• Structure (all phrases or sentences, start with verb or noun, etc.)

Evaluating Information

• Consider the source• Determine if information is consistent within the source and with other sources?

• Consider the study design

HealthNewsReview.org• When reporting about a treatment or test, be sure to:– Discuss cost– Describe how big (or small) are the potential benefits AND harms

– Use absolute (not just relative) risk/benefit data

– Compare the new idea with existing alternatives

– Seek out independent sources, with no conflicts of interest

– Look beyond the news release

HealthNewsReview.org (continued)

• When reporting about a treatment or test, be sure to:– Avoid disease mongering - exaggerating or medicalizing conditions

– Remember (and remind your readers) that not all studies are equal

– Note whether it’s really a new idea or just new wrapping on an old idea

– Explain whether/how widespread it’s available (or is it years away?)

Before we talk about risk, a a bit about

numbers• Do the math, if you can• Give a visual

– “size of a football field”

• Use comparable forms– 3/4 (fraction) vs. 75% (percentage) vs. 75 (absolute)

• Use sparingly– Only two sets of numbers per sentence

• Avoid excessive detail• Report only statistically significant numbers (or clarify)

Risk

• To the scientific community, risk is a statistical concept of probability– The likelihood that a given event will occur under certain circumstances

• For public, it is infused with emotion

When Presenting Risk• Clarify the outcome under consideration

– What are you talking about (getting disease vs. dying)?

– Is the outcome a composite or intermediate outcome?

– What is the time frame?

• Provide context– How dangerous (lethality)– Compare your risks to the average person– Compare this risk to other risks– Compare risks alongside benefits

When Presenting Risk (continued)

• Consider framing risk in more than one way– 1 out of 100 had X– 99 out of 100 did not have X

• State treatment alternatives• Review measures for controlling risk

• Highligh study limitations

Use Absolute Risk• Simplest way to represent results is by providing absolute event rates for the various exposure groups– Number who experienced outcome/number in group

– “The 10-year risk of death was 10% (10 in 100) in patients receiving drug A and 20% (20 in 100) in patients receiving placebo.”

• Give numerator and denominator if you can• Translate percentages less than 1 to frequencies (X in 1000) and use a constant denominator

Interpreting Absolute Risk

• No interpretation required– X out of 100 patients in the new drug group got sick compared with Y out of 100 patients in the placebo group.

What about relative risk?

• RR indicates the likelihood of developing a given condition.

• RR is the absolute risk in exposed / absolute risk in unexposed – Group A 10% (10 out of 100 got sick)– Group B 20% (20 out of 100 got sick)– (10/100) / (20/100) = 0.5 (50%)

Interpreting Relative Risk

• RR > 1.0 – exposure increases the chance of the outcome

• RR < 1.0 – exposure decreases the chance of the outcome

• RR = 1.0– exposure is not related to the outcome

Interpreting Relative Risk

• Relative risk < 1 (RR reduction)– 1- RR

• 1 - 0.6 = 0.40 x 100 = 40% lower• 1 - .23 = 0.77 x 100 = 77% lower

• Relative risk > 1 – RR - 1

• 1.25 - 1 = 0.25 x 100 = or 25% higher

– For RR greater than 2, just use the RR with “times the risk”• RR=2.5 (2.5 times the risk)

Relative Risk Pitfall• Well-described finding that RR appears more

impressive than corresponding absolute risk reduction

• Reporting relative risk reductions without specifying event rates leads readers to overestimate the magnitude of findingsStudy Group A

Event rate

Group BEvent rate

RR Reduction

Clinical Importance?

1 10% 20% 50% Yes

2 0.0001% 0.0002% 50% ?

Large samples make small effects statistically significant

Increases or Decreases Risk?

• RR = 0.8• RR = 10.0• RR = 1.5• RR = 0.4

Increases or Decreases Risk?

• RR=0.8 for heart disease following new therapy vs. controls– Patients taking new therapy have a __% higher/lower risk for heart disease than controls

• RR=10.0 for lung cancer in smokers vs. non-smokers– Smokers have __ times the risk for lung cancer as non-smokers

Increases or Decreases Risk?

• RR=1.5 for cancer in patients taking new drug versus those not taking it

• RR=0.4 for stroke in patients taking new drug versus placebo

When to Use Relative Risk?

• RR is an efficient way to summarize two numbers or make comparisons across treatments or studies– RR for death was 0.9 for drug X, 0.7 for drug Y, and 0.3 for drug Z. Unless absolute risks are given, RRs are

incomplete information about effect size

For All Risks

• Be clear about three things:– Exactly what the outcome is (having a heart attack)

– Over what time period the outcome occurred (5 years)

– In whom (adults with diabetes)

Activity

• Read the abstract of the provided study

• Together complete the RCT study worksheet

Homework• Reading assignment

– Gastel ch. 7 (pgs. 99-111)– “How do U.S. journalists cover treatments, tests, and procedures.”

• Writing assignment– Write a 250-word summary of a research study

– Summary is due by 5:30 pm, Feb. 24 by email

• No class next week, but homework still due