When is a trial valid?

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Geni Wren Veterinarians are inundated with studies, research, trials and data on everything from vaccine performance to antibiotic therapy. But how do you judge if a trial is valid?

At the winter Academy of Veterinary Consultants meeting, Bob Larson, DVM, PhD, Dipl. ACT, Dipl. ACVPM, Kansas State University, discussed determining how to critically evaluate feedlot studies, research and data. Larson used the example of looking at vaccines to prevent BRD.  

Internal validity is one of these criteria. This includes appropriate control of sources of bias, assures an unbiased estimate of the true direction and magnitude of the treatment effect in the study population, and random allocation, blinding, and consistent case-definition. “Internal validity is absolutely critical, to have a high strength of evidence to make a clinical decision at the feedlot level,” Larson says.

The research population is another important factor. Different research populations include target species (i.e. feedlot cattle) in similar housing and husbandry environments, target species in significantly different housing and husbandry environments and related species (i.e. sheep), unrelated species (rodents), or in vitro methods. “The highest strength of evidence is when we are looking at the target species (feedlot cattle) in similar housing and husbandry environments,” Larson explains.

A third component for deciding how strong a particular study is to make clinical decisions is to ask what did they measure as their outcome. “In my opinion for making a clinical decision, for example, about use of vaccines in feedlot cattle, the strongest outcomes I would like would be some herd-oriented outcomes such as morbidity risk, mortality risk, ADG, because they have direct clinical importance to me,” Larson says.



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