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What does having predictive value for human patients mean in medical practice?

The following excerpt is taken from the peer reviewed paper Are Animal Models Predictive for Humans? Niall Shanks, Ray Greek and Jean Greek, 2009; available here .

Excerpt from page 5:

By definition, when we speak of animals predicting human response in drug testing and disease research we are addressing the risks of wrong predictions and how much risk society is willing to tolerate. Troglitazone (Rezulin™) is a good example of the margin of error for medical practice tolerated in society today. Troglitazone was taken by well over 1 million people with less 1% suffering liver failure, yet the drug was withdrawn because of this side effect [33]. (Interestingly, animal studies failed to reproduce liver failure from troglitazone [34].) Rofecoxib (Vioxx™) is another example of the small percentage of morbidity or mortality tolerated in the practice of medicine vis-à-vis introducing a new drug. Figures vary, and are controversial, but it now appears that apparently less than 1% of people who took rofecoxib experienced a heart attack or stroke as a result, yet it was also withdrawn [35]. This means that even if a test with a PPV of .99 had assured industry that rofecoxib and troglitazone were safe, the test would not have been accurate enough for society’s standards. This is an important point. Medical practice does not tolerate risks (probability of being wrong) acceptable in some experiments conducted in labs. In basic research we might proceed with a study based on the outcome being more likely than not. For basic research this is acceptable. However, getting the answer wrong in medical practice has consequences; people die. Societal standards for medical practice today demand very high sensitivity, specificity, PPV and NPV from its tests. We will apply the above to animal models shortly.

References

33. FDA panel recommends continued use of controversial diabetes drug. http://www.cnn.com/HEALTH/9903/26/rezulin.review.02/index.html

34. Masubuchi Y: Metabolic and non-metabolic factors determining troglitazone hepatotoxicity: a review. Drug Metab Pharmacokinet. 2006, 21: 347-356. 10.2133/dmpk.21.347View ArticleGoogle Scholar

35. Topol EJ: Failing the public health – rofecoxib, Merck, and the FDA. N Engl J Med. 2004, 351: 1707-1709. 10.1056/NEJMp048286View ArticleGoogle Scholar

To read the paper in full please visit this link.

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