Dr. Greek Responds to Critics

[Letters to the Editor]

Dr. Greek Responds to Critics

As a coauthor of the article Animal and Medicine: Do Animal Experiments Predict Human Response (Vol. 13 No. 3) I would like to address the concerns raised by Conn and Parker (Vol. 13 No. 4).

Our article described the evidence, mainly from evolutionary biology, genetics, and clinical studies that animal models fail to be predictive for human response. The studies we quoted were not anecdotal but rather legitamate scientific studies. We presented numerous studies, sensitivity and positive predictive values when available, as well as numerous examples. The individual cases we cited were also from the scientific literature and were used as examples of the principle that different species respond differently to the same stimuli, specifically drugs and disease. We also tied all the above to theory as one should do in science.

Conn and Parker cited the 2000 Olson et al study (Regul Toxicol Pharmacol 2000 Aug;32(1):56-67). It was sponsored by the pharmaceutical industry and concluded animal models had a high concordance with humans. In other words, Olson et al measured sensitivity but not specificity, positive or negative predictive values. All four are needed to make assertions about prediction. The Olson et al even concluded: “This study did not attempt to assess the predictability of preclinical experimental data to humans.” This statement combined with lack of the three other values calls into question Conn and Parker’s position that the study proves animals have “significant predictive power”

It is easy to find high values for sensitivity, for example every human carcinogen has been found to be carcinogenic in some animal species; a sensitivity of 100%. But without knowing specificity, positive and negative predictive values, a high sensitivity alone is not synonymous with prediction and in most cases it is not even useful. Coulston and Shubick reported in 1980 in Human Epidemiology and Animal Laboratory Correlations in Chemical Carcinogenesis that there were “1600 known chemical carcinogens for mice and rodents in general. But there are only approximately 15 known to ever cause cancer in man.” That translates to a positive predictive value of around 1%.

Ad hominem attacks are the last refuge of those who can’t effectively argue a position. The accusation that I shared a podium with Jerry Vlasak and Kevin Kjonaas at a 2007 animal rights conference is untrue. I did not speak at any animal rights conferences in 2007. Dr Vlasak was on the science advisory board for Americans For Medical Advancement (AFMA) until his statement on killing vivisectors, which occurred sometime around 2004. He was asked to leave at that time and did. Further, in all of 2007, Kjonaas was in federal prison; not lecturing with me anywhere. However, even if the accusations were true they would have nothing to do with the scientific issues.
As to the accusation of taking statements out of context, I can only say we stand behind our work and the references are readily available.

Finally, AFMA is a not-for-profit that focuses exclusively on the scientific merits of animal models in science. There are areas where animals are very useful in science and areas where they are not. We explore the differences between the two.

—Ray Greek, MD., President, Americans For Medical Advancement