Wednesday, March 6, 2013

The Blood Thinner Pradaxa: What Type of Risk Was Reported?

plaricci plaricci 2 35 2013-03-05T01:43:00Z 2013-03-06T20:57:00Z 2013-03-06T20:57:00Z 1 597 3407 28 7 3997 11.9999

This blog post is the 2nd in a series aimed at helping the public, patients, physicians, health care providers, policy makers, and media professionals evaluate medical research findings presented in the media. I believe that a discerning public is an essential element of improved health care. All of us need to be on the same page as we evaluate, report, and make decisions about medical care and policy. This series of essays is not aimed at presenting opposing opinions but intended to painlessly teach readers some of the concepts of clinical epidemiology1 in order to empower readers to better judge and utilize medical information in the news and in advertisements. Interesting media reports and advertisements will be critiqued to instruct readers.


Utilizing a television commercial for the relatively new blood thinner, Pradaxa, I will expand upon the importance of asking the question
 “Are they talking about the risk difference or the relative risk reduction?” whenever we hear or see a medical report in the news or in a commercial.

A TV commercial stated that Pradaxa (dabigatran) reduced stroke risk more than the standard blood thinner (warfarin) by 35%.  Please view the one minute and 15 second commercial by clicking:

The commercial did not comment on the type of percentage quoted. According to textbooks of epidemiology the risk difference percentage is more important in regard to the everyday practice of medicine and public health policy than is the relative risk reduction5-8 percentage. The 35% reported in the commercial was the relative risk reduction percentage. The risk difference percentage was 0.6%.14,15 As you can see there is a big difference between 35% and 0.6%. The reporting of the different types of percentages can affect the way decisions are made.

At this point I will expand on the use of the risk difference by introducing the concept of Number Needed to Treat (NNT).10-11,16-17 "The Number Needed to Treat (NNT) is the number of patients you need to treat to prevent one additional bad outcome (death, stroke, etc.)."17 The number needed to treat is calculated from the risk difference. Therefore it is applicable to the everyday practice of medicine and public health policy. The ideal number needed to treat is equal to 1. In other words for a treatment to prevent disease or successfully treat disease, we need to treat only one patient. The closer the number needed to treat (NNT) is to 1 the greater the success rate. In the trial reported in the commercial the number needed to treat was 167.  In other words, in order to prevent one more stroke than those treated with warfarin an additional 167 patients would need to be treated with Pradaxa. The number needed to treat (NNT) was not reported during the commercial.  

At this point I reach out to you my readers with some ideas.  1. Those of you who are experts in areas that come up as stories in the various media e.g. credit cards, mortgages, constitutional law, etc., consider writing your own blog to interestingly educate all stakeholders in making informed decisions. Perhaps we can develop a collaborative network of 2nd opinions of ……… in the media. Naturally, the blog would need to provide documentation (in the form of references and links) of your statements so that readers could audit your statements. The documentation would be key to developing credibility. 2. Feel free to email me at with your suggestions and comments. Title your email: BLOG.  3. Let me know if you would like to collaborate or support me in the expansion of this blog. The long range goal is to have a daily posting on recent medical news in the media. Thank you in advance for your input.               

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