Numbers, Math and Communicating Risk “You want numbers? You can’t handle numbers!”
The FDA would like more risk information to be presented in direct to consumer (DTC) drug advertising (see “FDA Draft Guidance for Print DTCA: Less than Feared“). Some DTC experts want the drug industry to take the lead in communicating risk.

To make sense of trial data and risk information in DTC ads, you need to look at numbers. As pointed out in a recent Washington Post article, “many people don’t demand the same kinds of numbers [as they do with money matters] when judging medical findings.” To paraphrase Jack Nicholson in the 1992 movie A Few Good Men, “You want numbers? You can’t handle numbers!”

This article examines the numbers from Vioxx trials to illustrate how difficult it may be to communicate risk and benefit to consumers.


Sometimes, not all the critical data from a trial are available and you need to do some math to calculate risk. Here’s an example from a recent article published in the press (I won’t reveal the source because I want you to do the math).

  • There were 2,643 people in a study comparing naproxen to Celebrex. 702 took naproxen, 1057 took placebo, 704 took Celebrex.
  • There were a total of 70 cardiovascular events among all the study participants.
  • The proportion of people having an event was 50% higher in the naproxen group compared to placebo.
  • There was no increased risk for people taking Celebrex compared to placebo. You can assume that the Celebrex risk was the same as the placebo risk.

Q1: Calculate the likely magnitude of the naproxen risk, i.e., what percent of people taking naproxen experienced a cardiovascular event compared to people taking placebo?

Q2: What would these numbers be if no (0) people taking Celebrex in this trial experienced a cardiovascular risk?

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Update (December 2011): See the blog post and article below for a follow up on this issue. Also, to address a requirement of the 2010 Patient Protection and Affordable Care Act (Affordable Care Act), FDA may be required to revisit this issue (see “FDA Summary of Drug Benefits vs Risks“).–>

Issue: Vol. 4, No. 2: February 2005
Word Count: 1257

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