As scientific experiments, clinical trials are designed to uncover evidence that a tested treatment will work for patients, and will improve patients' chances for a cure or a way to manage disease or a medical condition. By definition, scientific experiments are expected to be objective and impartial. It would seem, then, that evidence-based medicine (EBM), determined by the outcomes of clinical trials, would be an objective decision-making tool to help patients and their doctors make treatment decisions, once a patient has been diagnosed.
But the use of evidence-based results are not always so clearly usable. Evidence-based medicine, with its roots in clinical trials, attracts some controversy over accuracy, its application, its objectivity and whether or not it should be used as the basis for treatment decision-making.
How Does Objective Scientific Discovery Create Controversy?
Actually -- that's just the point. Some professionals will tell you there is too little objectivity in clinical trials and bio-scientific experiments. In fact, the controversies over the objectivity of evidence-based medicine stem from three points:
- The evidence is gathered using groups of people, not individuals.
- Not all patients have the same set of values.
- There may be built-in biases in the way the experiments are designed, too often based on a profit motive.
1. Evidence is developed based on group results, and not individual results.
When a clinical trial is designed, it focuses on a group of people who have similar characteristics, and attempts to prove it works to achieve a specific outcome.
For example, a drug might be tested on a group of men age 50 to 75 who have heart disease, with a goal of determining whether that drug helps them prevent a heart attack. At the conclusion of the trial, it may be shown that among the men who took the tested drug, 60% of them had no heart attack, and among the 40% who did have a heart attack during the trial, 75% of them survived the attack. That means that for every 100 men in the trial, 90 of them survived the trial.
Cardiologists and other doctors might agree that the evidence of that trial suggested that the drug might be a good choice for staving off a deadly heart attack among men age 50 to 75. If you fit that profile, there would seem to be good evidence that the drug tested would help you live longer if you took it, too.
However, the opponents of EBM will point out that 10 men died. If you are one of the 10 men, or one of their loved ones, the drug failed. Those people would tell you that since the drug failed, the evidence shows it is not a good choice for men who fit that profile.
Another point of dispute based on the group approach would be the profile of the men, and whether it could be generalized. Some professionals might suggest that the drug only worked for white men and would not be appropriate for men of color. Others would group all men of all races into their consideration of the evidence.
Age needs to be considered, too. If it worked well for men between the ages of 50 and 75, does that mean the evidence would be generalized to its effectiveness for men who are 45? or 49? Or 80?
Would it work for women? Some professionals would use this evidence to say yes. Others would say no. It has only been in the past dozen years or so that womens' heart disease has been regarded differently from heart disease in men.
Further, there may be other evidence that a different drug was even more effective, therefore, even though this one seemed to be effective for 90% of the men who took it, another one might show evidence of effectiveness for 95%.
Finally, some professionals will dispute evidence if they feel there were not enough people tested or not enough time passed. Results and conclusions drawn from a group of 5,000 should be more accurate than if only 200 people participated in the trial. A trial that lasted two years might be considered more accurate than one that lasted only six months.
2. Not all patients have the same set of values.
Evidence-based medicine is based on science. But when human beings need to make decisions about their treatment, they may consider the evidence in different ways based on their values. That means the evidence is not as objective patient-by-patient as all researchers might consider it to be.
When recommendations are being made based purely on the evidence, there is no room for a patient's values because values can't be evaluated in the same objective way.
For example, a woman may discover she has breast cancer. There may be evidence that supports a specific chemotherapy treatment for her that will help her destroy the cancer, or put her into remission. Her doctor might recommend that evidence-based treatment as her best chance for recovery from her breast cancer.
Under ordinary circumstances, she might decide that treatment gives her the best chance of survival. But what if she is pregnant? That changes the dynamic, and while science might tell her that she can be saved, she knows she needs to take her fetus into account before she makes her decision. Her choice may be to save herself and lose her pregnancy, or to save the baby and risk her own life, or perhaps the evidence shows both are at risk, or neither is at risk. She may have to delay the treatment knowing that it will affect the fetus, but of course, that may remove her from the window of opportunity for the treatment's best chance of helping her.
The evidence may not have been gathered for pregnant women (and often isn't) -- but will her doctor be like some of the doctors described in question one above, suggesting that the evidence be looked at in a broader group?
And what are her husband's values? Or her parents' values?
Evidence-based medicine makes no room for value judgments. Most medical professionals realize that a patient's values must be taken into account when treatment decisions are made, even though they are not accounted for in EBM.
In Part II, we will consider how conflicts of interest may affect the design of clinical trials, and therefore their outcomes.
