Reporting of Results from Animal Studies
Authors: Hugh A. Tilson, Jane C. Schroeder
Journal: Environmental Health Perspectives (2013)

One of the key elements of the scientific process is reproducibility: Experimental results generated in one laboratory must be repro ducible by others working independently.Therefore, it is of concern to us as editors of a major scientific journal to learn that only 6 of 53 "landmark" preclinical cancer studies could be reproduced (Begley and Ellis 2012).In addition, Prinz et al. (2011) reported that almost twothirds of 67 inhouse preclinical cancer projects did not replicate data previously published by others.These observations are based on preclinical cancer studies, and it is not known how pervasive this problem may be in other disciplines, including environmental health research.Vasilevsky et al. ( 2013) pointed out that the reproducibility of scientific research depends in large measure on whether the "materials and methods" of a paper are described such that other investigators are able to independently replicate effects observed in the original study.Unfortunately, the degree to which sufficient methodological details are provided can be problematic.For example, Kilkenny et al. (2009) published the results of a systematic review of original in vivo research involving laboratory animals.Of the 271 papers they evaluated, only 60% provided information about the number of animals used or described in detail the species, strain, sex, age, or weight of the animals.The authors also noted that about 30% of the papers lacked sufficient details concerning the statistical analyses.Findings such as these indi cate that the lack of methodological detail could be a major barrier to subsequent attempts to replicate the work of others.According to Ransohoff and Gourlay (2010), "any study's reliability is determined by [the] investigators' choices about critical details of research design and conduct."Some choices could lead to bias or the "systematic erroneous association of some charac teris tic with a group in a way that distorts a comparison with another group" (Ransohoff 2005).Key approaches to reduce bias include the randomization of groups and blinding (Krauth et al. 2013).However, randomization and blinding are not used universally in preclinical research.Van der Worp et al. (2005) reported that fewer than half of the 45 pre clinical studies they reviewed included randomization of treatment, blinded adminis tration of treatment, and blinded outcome evaluation.In addition, Kilkenny et al. (2009) found that most papers they surveyed did not use randomiza tion or blinding.Addressing concerns about the reproducibility of research find ings will require cooperation and collaboration from major segments of the scientific community.From our perspective, it seems clear that many authors are not sufficiently trained in experimental design or the importance of controlling for sources of bias in their studies.We believe that courses on the principles of experimental design should be included at the graduate level.Many academic departments and govern mental institutions now require students and employees to take courses on ethics.We believe that it is equally important to train stu dents and young investigators about experi mental design and how to be trans parent in reporting their results in the peerreviewed literature.In addition, we believe that it is important for study sections and funding agencies to critically evaluate experimental designs described in grant proposals under considera tion.Finally, journals can be more proactive by insisting that critical methodo logi cal details be included in papers submitted for possible publication.