Over the last several months, we’ve shared with you concerns from the scientific community about the validity of animal experimentation. Previously, we discussed widespread reproducibility issues, which often stemmed from problems with the design and execution of animal experiments.
This week’s Science First highlights issues that arise from animal attrition, or the loss of animals during an experiment. Just how prevalent is attrition in preclinical research, and what consequences does it have on the outcome of an experiment? Do scientists adequately report and explain why animals have been dropped from a study?
To gain insight to these questions, researchers in a recent study used a two-pronged approach. First, they used computer simulations to examine the impact of random loss of animals in experiments versus biased removal. They learned that loss of even a few animals in an experiment can significantly distort true effects. Nonrandom removal, which may occur because of subconscious bias, resulted in a great inflation of how effective a treatment appeared to be.
Next, they selected a sample of 100 preclinical cancer and stroke studies, which included 522 experiments, to examine the frequency and impact of attrition. They compared the number of animals mentioned in the methods section to those reported in the results. In 67% of experiments, it was impossible for researchers to compare animal numbers, often because the studies did not mention animal numbers in one of the sections or because they mentioned them in a non-transparent way (i.e. as a range of values rather than a number.)
Of the experiments for which animal numbers were reported, 31% indicated that animals had been dropped from the study, with only a quarter of those studies providing an explanation for animal loss. Failure to report how many animals have been dropped from a study, or to explain why they have been dropped, can significantly bias the results of a study.
Despite the tremendous cost of preclinical studies, laboratory findings often fail to translate to the clinic. Issues regarding the transparency of animal experiments and how scientists report their results certainly are contributing factors, as is the lack of predictive value of animal models themselves.
Continued investment in flawed animal studies wastes time, resources and animal lives, and studies such as these highlight the need for the research community to move toward modern, human-relevant, non-animal testing approaches that can advance science without harming animals.
What are your thoughts on this week’s Science First? Send your questions and comments to firstname.lastname@example.org. I look forward to hearing from you.
-Dr. Pam Osenkowski, Director of Science Programs
Missing mice: gaps in data plague animal research
January 5, 2016
Reports of hundreds of biomedical experiments lack essential information.
For more information see: Nature