Medical research that uses animals to test therapiesfor human brain disorders is often biased, claiming positive results andthen failing in human trials, US researchers said Tuesday.
|Lab mice are seen in Sao Paulo, Brazil on November 5, 2001.|
The findings by John Ioannidis and colleagues at Stanford Universitycould help explain why many treatments that appear to work in animals donot succeed in humans.
Bias also wastes money ad could arm patients in clinical trials, said the study in PLoS Biology.
Researchers examined 160 previously published meta-analyses of 1,411animal studies on potential treatments for multiple sclerosis, stroke,Parkinson’s disease, Alzheimer’s disease and spinal cord injury, alldone on more than 4,000 animals.
Just eight showed evidence of strong, statistically significant associations using evidence from more than 500 animals.
Only two studies seemed to lead to “convincing” data in randomized controlled trials in humans, it said.
The rest showed a range of problems, from poor study design, to smallsize, to an overarching tendency toward publishing only studies inwhich positive effects could be reported.
Statistically, just 919 of the studies could be expected to showpositive results, but the meta-analysis found almost twice as many –1,719 — that claimed to be positive.
“The literature of animal studies on neurological disorders is probably subject to considerable bias,” concluded the paper.
“Biases in animal experiments may result in biologically inert oreven harmful substances being taken forward to clinical trials, thusexposing patients to unnecessary risk and wasting scarce researchfunds.”
Animal studies make up a “considerable portion” of biomedicalliterature, with some five million papers archived in the medical PubMeddatabase, it said.
While animal research exists to test safety and efficacy before newtreatments are attempted in humans, most interventions fail when theyreach human clinical trials, said the researchers.
“Possible explanations for this failure include differences in theunderlying biology and pathophysiology between humans and animals, butalso the presence of biases in study design or reporting of the animalliterature.”
Researchers said the bias likely originates when scientistsconducting the animal studies choose a way of analyzing the data thatappears to give a better result.
Also, scientists tend to seek out high-profile journals to publishtheir work, and those journals tend to prefer studies with positiveresults.
Solutions may include stricter guidelines for study design andanalysis, pre-registration of animal studies so that the results must bepublished whether positive or negative, and making raw data availablefor other scientists to verify, the study said.