Health and Medical News and Resources

General interest items edited by Janice Flahiff

Poorly presented risk statistics could misinform health decisions

Poorly presented risk statistics could misinform health decisions

From the March 15 Eureka news alert item

Choosing the appropriate way to present risk statistics is key to helping people make well-informed decisions. A new Cochrane Systematic Review[abstract]*** found that health professionals and consumers may change their perceptions when the same risks and risk reductions are presented using alternative statistical formats.

Risk statistics can be used persuasively to present health interventions in different lights. The different ways of expressing risk can prove confusing and there has been much debate about how to improve the communication of health statistics.

For example, you could read that a drug cuts the risk of hip fracture over a three year period by 50%. At first sight, this would seem like an incredible breakthrough. In fact, what it might equally mean is that without taking the drug 1% of people have fractures, and with the drug only 0.5% do. Now the benefit seems to be much less. Another way of phrasing it would be that 200 people need to take the drug for three years to prevent one incidence of hip fracture. In this case, the drug could start to look a rather expensive option.

Statisticians have terms to describe each type of presentation. The statement of a 50% reduction is typically expressed as a Relative Risk Reduction (RRR). Saying that 0.5% fewer people will have broken hips is an Absolute Risk Reduction (ARR). Saying that 200 people need to be treated to prevent one occurrence is referred to as the Number Needed to Treat (NNT). Furthermore, these effects can be shown as a frequency, where the effect is expressed as 1 out of 200 people avoiding a hip fracture.

In the new study, Cochrane researchers reviewed data from 35 studies assessing understanding of risk statistics by health professionals and consumers. They found that participants in the studies understood frequencies better than probabilities. Relative risk reductions, as in “the drug cuts the risk by 50%”, were less well understood. Participants perceived risk reductions to be inappropriately greater compared to the same benefits presented using absolute risk or NNT.

“People perceive risk reductions to be larger and are more persuaded to adopt a health intervention when its effect is presented in relative terms,” said Elie Akl of the Department of Medicine, University at Buffalo, USA and first author on the review. “What we don’t know yet is whether doctors or policymakers might actually make different decisions based on the way health benefits are presented.”

Although the researchers say further studies are required to explore how different risk formats affect behaviour, they believe there are strong logical arguments for not reporting relative values alone. “Relative risk statistics do not allow a fair comparison of benefits and harms in the same way as absolute values do,” said lead researcher Holger Schünemann of the Department of Clinical Epidemiology and Biostatistics at McMaster University in Ontario, Canada. “If relative risk is to be used, then the absolute change in risk should also be given, as relative risk alone is likely to misinform decisions.”

 

***  For suggestions on how to get this review for free or at low cost click here

Cochrane Reviews are ” systematic reviews of primary research in human health care and health policy. They investigate the effects of interventions (literally meaning to intervene to modify an outcome) for prevention, treatment and rehabilitation. They also assess the accuracy of a diagnostic test for a given condition in a specific patient group and setting.”

Please go here for a previous posting on Cochrane Reviews.

 

March 22, 2011 Posted by | Medical and Health Research News | , , , , , , | Leave a comment

Cochrane Reviews – A Great Source for Sound Medical Evidence

Cochrane Reviews are thorough unbiased detailed systematic reviews of research in both human health care and health policy.

Some Cochrane Reviews investigate whether or not an intervention (as an antibiotic) really produces a specific intended effect (as reducing sore throat symptoms).

Other Cochrane Reviews look for evidence that a diagnostic test is accurate for a given disease within a specific patient group.

Evidence is largely based on clinical trials.

All Cochane Reviews address specific narrowly defined questions. Each review is the product of a independent team of health care and information professionals (as librarians). These scientific reviews are the result of many hours of analyzing original research. Each review can take up to two years to publish.

While there are presently over 4000 Cochrane Reviews, the Review collection does not cover every possible intervention, drug, or diagnostic test.

However, the abstracts of all reviews are available to the public. Many have plain language summaries.

(For suggestions on how to get free full text of Cochrane Reviews, please click here).

How to search for Cochrane Reviews

**Go to Cochrane Reviews- Explore

**Search for reviews using the simple search at the page or the advanced search option.

The Cochrane Review Home page contains informational links, including

**The Top 50 reviews (Past 24 hours, 7 days, and 30 days)

**Special Collections from the Cochrane Library

**Cochrane Library Editorials

January 25, 2011 Posted by | Finding Aids/Directories, Librarian Resources | , , | Leave a comment

Call for clinical trial raw data to be freely available to all (& a related call from the scientific community)

A recent BMJ editorial (Goodbye PubMed, hello raw data) ****calls for clinical raw data to be freely available to everyone.
The author cites the example of  the influenza drug oseltamivir manufactured by Roche.

Reviewers for Cochrane Reviews asked Roche to release clinical trial data so they could systematically and comprehensively review antivirals as flu treatments. Roche refused, leaving the reviewers with inadequate incomplete information to complete their analysis.

The editor ends his article with these paragraphs…

From now on, they say, reviewers must have access to all unpublished data, not only from unpublished trials—the usual focus of concern about publication bias—but also from those that have been published in peer reviewed journals. Reviewers must assess entire trial programmes, and so new tools and methods are needed. If the trial reports are incomplete, reviewers should turn to reports from the drug regulators. As Tom Jefferson, the lead author for the Cochrane review, told me, “it’s goodbye PubMed, goodbye Embase.”

The reviewers have posted their new style protocol for this review on the Cochrane site and, recognising the enormity of the task, they are recording how much work is involved. But it must be clear to everyone that such a heroic approach is unsustainable across the whole of healthcare, given the resource constraints on academics and regulators. Which brings us back to what seems to be the only real solution—that the raw data from trials must be made freely available. Journals clearly have a role to play in making this happen, as An-Wen Chan agrees in his editorial (doi:10.1136/bmj.d80). The International Committee of Medical Journal Editors meets in a few months’ time. This will be on the agenda.

Scientists also see the need for access to research data.
The entire 2011 January/February issue of D-Lib Magazine is devoted to this topic.
**Cochrane Reviews are part of the Cochrane Collaboration, which
strives to provide the best evidence for health care. Cochrane reviews involve specific interventions in a specific clinical context, as antivirals for flu prevention in healthy adults. Individual reviews involve extensive literature research performed by independent teams of professionals.

Most reviews are only available through a paid subscription to the Cochrane Collaboration. However, many medical and academic libraries subscribe to the Cochrane Collaboration. Contact an academic reference librarian to see if they subscribe and if they provide access to the public.

****Via a MedLib posting by medical librarian Susan Fowler

 

January 20, 2011 Posted by | Biomedical Research Resources, Finding Aids/Directories, Medical and Health Research News, Professional Health Care Resources | , , , , , , , , | Leave a comment

   

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