{"id":2986,"date":"2009-08-14T08:30:22","date_gmt":"2009-08-14T13:30:22","guid":{"rendered":"http:\/\/pmedicine.org\/epatients\/?p=2986"},"modified":"2009-08-17T11:00:35","modified_gmt":"2009-08-17T16:00:35","slug":"e-patient-training-topic-a-national-article-reports-relative-risk-not-raw-data","status":"publish","type":"post","link":"https:\/\/participatorymedicine.org\/epatients\/2009\/08\/e-patient-training-topic-a-national-article-reports-relative-risk-not-raw-data.html","title":{"rendered":"e-Patient Training Topic: National Article Reports Relative Risk, Not Raw Data."},"content":{"rendered":"

Important update: it turns out the writer did<\/strong> get it right, and this was an editing error at the Boston Globe. See my comment August 17.<\/em><\/p>\n

—–<\/p>\n

As empowered, engaged patients we have a responsibility to evaluate the articles we read. A case in point is this week\u2019s Associated Press article Any\u00a0Spread Of Breast Cancer Raises Risk Of Return<\/a><\/strong>. It\u2019s about a paper in this week\u2019s New England Journal of Medicine<\/em> that found a 50% increase in the chance of cancer recurring, and quotes an expert as saying<\/p>\n

\u201cI think it will influence treatment. If we\u2019re considering treating the patient, we probably should.\u201d<\/p><\/blockquote>\n

Can you spot the flaw in that reasoning, if all you have is that number? That\u2019s\u00a0all the article reported, and that’s a problem.<\/p>\n

The problem is relative risk reduction<\/strong>. As we discussed last November in Making sense of health statistics<\/a>, relative risk is an unsound basis for policy decisions, because you can\u2019t tell the actual size of the impact. That\u00a0affects you as a patient and you as a citizen thinking about policy.<\/p>\n

In the study, did the 50% change mean represent a change from 200 patients per thousand to 300 per thousand, or from 2 per thousand to 3 per thousand? (Specifically, if we spend a zillion dollars based on this result, will we affect 1\/1oth of the US population, or 1\/1,000th?<\/p>\n

Think about it for your own body. Your health provider suggests a treatment and says it\u2019ll reduce your chance of a problem by 35%. (That\u2019s the number commonly cited for statins like Lipitor.) Sounds impressive, right? But that\u2019s a relative risk<\/strong> number. The raw data showed that among the general population, 1.59% had a coronary event, and among Lipitor users, 1.02% had one anyway<\/em>. So for the $25 billion we spend on Lipitor in the US, we affect one patient in 200.<\/p>\n

So now imagine your provider says \u201cThere\u2019s a one in 200 chance this prescription will make a difference for you. Want it?\u201d<\/p>\n

I think there are two levels of concern for us as patients engaged in the new world of healthcare:<\/p>\n