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Open Access

Are animal models predictive for humans?

Philosophy, Ethics, and Humanities in Medicine20094:2

https://doi.org/10.1186/1747-5341-4-2

Received: 23 July 2008

Accepted: 15 January 2009

Published: 15 January 2009

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Archived Comments

  1. Erratum

    28 August 2009

    Ray Greek, Americans For Medical Advancement

    Dr Andrew Knight was kind enough to notify us of several errors we made in quoting from Knight et al. cited as reference 43 in our in our section entitled Carcinogenesis (pp. 8-9). We apologize to Drs Knight, Bailey, and Balcombe and wish to correct the errors at this time.

    On page 8 of the paper we state:

    "According to Knight et al. [43] as of 1 January 2004, IRIS was unable to classify the carcinogenic status of 93 out of 160 chemicals that had been evaluated only by animal tests."

    Concerning this claim Dr Knight has made the following comments (email communication):

    "Unfortunately, this statement is actually incorrect. The EPA did indeed provide a human carcinogenic classification for many of these chemicals, and I did not state otherwise in my paper [43]. Allow me to explain:

    "Of the 543 chemicals catalogued in the EPA’s IRIS chemicals database at the time of my study, 235 had been assigned human carcinogenicity classifications. Of these, 17 were classified as definite or probable human carcinogens on the basis of their human carcinogenicity data. Of the remaining 218 chemicals lacking even limited human data, 160 were associated with animal carcinogenicity data (these are the 160 on which my study focused, and to which you refer).

    "64 of these were assessed by the EPA as probable human carcinogens, and three were considered probably not carcinogenic to humans. The remaining 93 chemicals were considered unclassifiable as to their human carcinogenicity (53) or to be possible human carcinogens (40) , based on animal data considered inadequate to support a stronger classification.

    "The key point, which I emphasized in my paper, is that in a majority of cases (58.1%; 93/160), the EPA considered animal carcinogenicity data inadequate to support a classification of probable human carcinogen or non-carcinogen. These are clinically useful human carcinogenicity classifications.

    "As you can see, however, in 40 of these 93 cases, the EPA did consider the animal data sufficient to classify the chemical as a ‘possible human carcinogen.’ However, I not consider this classification to be clinically useful, in comparison to ‘probable human carcinogen’ or ‘non-carcinogen.’ Hence, my results demonstrate that in the majority of cases, the EPA considered the animal data insufficient to deliver human carcinogenicity classifications of significant clinical use, rather than no classifications at all – as your statement asserts."


    By “carcinogenic status” from our quote we meant categorization that is clinically useful e.g., either human carcinogen or non-carcinogen. As Dr Knight has pointed out, he does not consider the classification “possible human carcinogen” to be clinically useful either. We apologize for any ambiguity in our original statement.

    Further on page 8 we quoted Knight et al as follows:

    "For the 128 chemicals with human or animal data also assessed by the human carcinogenicity classifications were compatible with EPA classifications were compatible with EPA classifications only for those 17 having at least limited human data (p = 0.5896) [43]."

    It should read:

    "For the 128 chemicals with human or animal data also assessed by the IARC human carcinogenicity classifications were compatible with EPA classifications only for those 17 having at least limited human data (p = 0.5896). [43]"

    We left the word IARC out of the sentence. This was a transcriptional error and we apologize for them.

    On page 9 we quoted Knight et al as follows:

    "... based on these IARC figures, the positive predictivity of the animal bioassay for definite of probable human carcinogens was only around 7% (104/502), while the false positive rate was a disturbing 79.3% (398/502) [43]."

    The above should be:

    "... based on these IARC figures, the positive predictivity of the animal bioassay for definite or probable human carcinogens was only around 20.7% (104/502), while the false positive rate was a disturbing 79.3% (398/502) [43]."

    We mistakenly said of instead of or in the second line and 7% instead of 20.7% . These were transcriptional errors and we apologize for them.

    Finally on page 9 we state:

    "More-recent IARC classifications indicate little movement in the positive predictivity of the animal bioassay for human carcinogens. By January 2004, a decade later, only 105 additional agents had been added to the 1993 figure, yielding a total of 885 agents or exposure circumstances listed in the IARC Monographs [46]. Not surprisingly the proportion of definite or probable human carcinogens resembled the 1993 figure of 13.3%. By 2004, only 9.9% of these 885 were classified as definite human carcinogens, and only 7.2% as probable human carcinogens, yielding total of 17.1%."

    This is, in fact, a continuation of the previous quotation but the indentation was moved left during our editing process. This was our mistake and we apologize.

    We thank Dr Knight for bringing these matters to our attention.

    Competing interests

    Original coauthor

Authors’ Affiliations

(1)
Department of History, Wichita State University
(2)
Americans For Medical Advancement

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