I have had the same family doctor for 28 years. When I have an ailment, I expect that he will be up to date on the latest scientific data on the treatment, management, and prevention for my problem. I expect that he will have attended conferences on a regular basis, kept current with the medical literature, be fully appraised of older medications that no longer work or cause problems, and be aware of the new medications on the market. Although I do not wish to be the “guinea pig” in his practice, I understand that I may be one of the first people for whom he has prescribed a new product. When this happens, I want to be given that information so that I can make an informed decision about whether I want the new or old medication. I also assume that no matter what medication I am given, it is my obligation to tell him when the medication did not work. Finally, I expect to be referred to a specialist or to another doctor for a second opinion if my own doctor is not confident to manage my problem.
Even though I expect a lot of my doctor, I also take ownership for my own health. As an informed consumer, I typically have a list of differentials and know what medications are used for the problem before I go to the doctor. This past summer I did something rather foolish. I went canoe camping with insufficient water-treatment tablets, and when the tablets ran out, I did not boil the water thoroughly. Two days after leaving the park I experienced the severe headaches and vomiting of clinical giardiasis. When I arrived at the hospital, I told the attending physician that I had giardiasis and was able to ask for metronidazole when he said “I’m not sure what to treat that with.”
Nutrition is a key component of health, and although I like chocolate too much to stick to a perfect diet, I do like to keep informed. I subscribe to the Nutrition Action Newsletter1 that is published by the Center for Science in the Public Interest. Each issue provides a review of the most current research on a specific link between health and diet. For example, there may be an issue focused on cancer or cardiac disease or on a food component such as fiber. The summaries state the associations proven by science, those found in preliminary studies needing more research, and those that are questionable because of variable research findings. The value I place in reading data that has been summarized by knowledgeable scientists leads me to a discussion about the relative value of data available to us as we try to keep up with the latest knowledge.
Systematic reviews are used frequently in human medicine to summarize all the known information about how to clinically manage a specific disease. Funding agencies focused on human health are willing to support researchers to complete these reviews. Systematic reviews are used infrequently in veterinary medicine. Most recently, they have been applied to understand the implications of animals, animal products, and production systems (or wildlife habits and habitat) for spread of zoonotic diseases to human populations. Hopefully, we will soon see funding agencies interested in similar reviews about issues related to veterinary medicine. Systematic reviews differ from literature reviews. Although learning to conduct a systematic review typically requires a 1-week course, I will present a brief description. A systematic review requires a rigorous literature search to ensure that all peer-reviewed literature, case reports, conference proceedings, white papers, and even lay literature are identified. Then, using strict criteria for quality control, each piece of literature is evaluated to determine whether or not it will be included in the final analysis. This evaluation is performed by two independent reviewers and results in a numeric score for each paper. Criteria for evaluation of the papers include such factors as equal likelihood of a person being in the treatment and control groups; relative representation of people by age, severity of illness, and socioeconomic status in the treatment and control groups; control for bias; clear definition of disease criteria; and complete follow-up of case and controls. Papers that are retained for the next phase of the review are included in the table representing the results of the intervention. If this were an evaluation of a medication (such as an antibiotic) for treatment of swine respiratory disease, the outcome measures would likely be mortality, days of treatment, average daily gain, and feed-to-gain ratio. On-farm studies including large numbers of animals (assuming they were randomly assigned to treatment in a side-by-side trial) would be weighted more heavily in the final analysis than a laboratory study conducted on six pigs. The researcher interprets the global results from the selected papers and concludes that the treatment does work, does not work, or only works under certain circumstances, or insufficient data is available and therefore more studies are required.
Where do you look for answers to the clinical questions that face you in practice? First, we can likely assume there are no currently published systemic reviews for your problem. The next best resource is a controlled field trial conducted as a side-by-side study. This implies that the researcher randomly assigned pigs (or pens of pigs) to treatment. For the same batch of pigs, some were treated and some were untreated, or some were treated with product A and others with product B. Ideally, the study will be triple blinded. This means that the researcher, the producer, and the statistician did not know which pigs received each treatment. This can be done in a number of ways but I will describe one. The researcher identifies all pigs with individual ear tags and weighs them before weaning. She then randomly assigns them to Treatment A or Treatment B according to weight and gender. Then another person determines which drugs to assign to treatments A and B and injects the pigs. The information about which treatment was given to each group is kept in a sealed envelope until the project is complete. The person looking after the pigs does not know their treatment status and therefore morbidity and mortality data cannot be biased by his expectations. Finally, the data is given to the statistician who analyses it, comparing Group 1 to Group 2, still not knowing which treatment was applied. Triple-blinded studies are uncommon, but are not difficult to conduct. It is important that we think about how to use them more frequently in veterinary medicine.
Case reports and case studies are also valuable starting points for either new clinical problems or new approaches to treat and manage clinical problems. They are the formal way in which experience from the field is recorded and scrutinized. I realize that veterinary practitioners are busy and publishing a report is very time-consuming. However, these reports, once scrutinized through the peer-review process, form a valuable record of our profession. They often provide the first record of a new disease. Without clinical-trial data, the practitioner must rely on case reports and studies.
There is an important distinction between what is published in a proceedings paper and a manuscript published in a peer-reviewed journal. The former has limited or no peer review and may represent the observations of one person, that upon reflection or challenge will be presented in a different manner. Very commonly, the peer-review process ensures that the conclusions of a paper are limited to the scope of the study or the case report, while the initial submission makes claims well beyond the work itself. When there is no information in the peer-reviewed literature, conference proceedings are key resources. Once there are papers in the peer-reviewed literature, it is recommended that we rely less on proceedings papers (as an aside, some may recall the days when JSHAP insisted that authors split their reference lists into those from peer-reviewed and non-peer-reviewed sources).
Experience is a key source of data for the practitioner. Through trial and error we learn what works “in our hands” and what fails. But do we always? How often does something not work and we do not hear about it? How often was the problem going to go away, or at least reach tolerable levels, despite our best efforts? I encourage each person reading this to set up trials with the producers who ask for our advice. My experience is that many producers are excited to do a trial to test out a new product on their farm. Too often I hear from veterinarians that the trial is not a “side-by-side” trial but rather a “one batch after the next” trial. I do not know how to interpret the results of those studies. In my experience, even without treatment, the clinical disease problem in one batch does not equal the clinical disease problem in the next batch. If we are dealing with an infectious disease outbreak, the problem is most likely to diminish on its own as the level of herd immunity increases. So, although I do put a high value on the experience of a practitioner, I also question conclusions that new treatments work when they have not been tested in a randomized, side-by-side trial.
The experience of the producer is also valuable. They are in the barn on a day-to-day basis and can share with us their observations and the way a treatment or management change works in their barn under their barn conditions. I appreciate hearing both the success stories and the failures of what I have recommended over time. These are key learning moments.
The expectations I have of my doctor make me think about what swine producers expect of us: keeping our knowledge base current, knowing what value to put on each piece of new information, and testing what we think we know by randomly assigning treatments to pigs or groups of pigs so we are not fooled by the success of time.
-- Cate Dewey, DVM, MSc, PhD
1. Center for Science in the Public Interest. Nutrition Action Newsletter. Available at: http://www.cspinet.org/nah/. Accessed 25 January 2012.