By James Dickinson, Harminder Singh, Roland Grad
Aseries of opinions published on healthydebate.ca assert that the Canadian Task Force on Preventive Health Care (Task Force) is flawed, and should be disbanded or reformed to include experts on each topic addressed. The authors assert that Task Force recommendations are out of date and use out-of-date evidence. These advocates understandably want the issues of interest to them to be vigorously addressed.
Experts practising in any field see the worst cases of “their disease,” be it cancer, blindness, mental disorder, heart attacks or strokes, and want to prevent that – an understandable emotional reaction. They want to increase the sensitivity of testing and expand the ages or other criteria for screening to ensure no one is missed.
However, those without epidemiology background have difficulty understanding that increasing sensitivity comes at a cost, whether decreasing specificity (i.e., false positive tests), increased exposure to harms of screening, or diversion of resources from other endeavours. The writers of these opinion pieces appear unaware why the Task Force is formulated the way it is, how it uses evidence and reaches its conclusions.
Conflict of interest is a major issue in guideline development. The authors surprisingly assert that the only reason to exclude experts is to prevent financial conflict of interest, and that this is unimportant in Canada because screening activities do not directly benefit specialists. Over a long history, many guidelines from specialty societies have recommended more interventions that have resulted in referrals and work for those specialists, leading to overdiagnosis, overtreatment and increased health-care costs.
Conflict of interest also includes strong, preconceived opinions/research interests that can lead to biased assessment of evidence. Therefore, many groups have produced “guidelines for guidelines” to reduce conflicts of interest and ensure their scientific validity. The Canadian Medical Association Journal follows such policies.
In public decisions, one of the greatest difficulties is determining who is an “expert.” Many people who research a topic have strongly held beliefs derived from prior ideas, not necessarily from evidence. Their research and analysis are influenced by prior beliefs. The “experts” nominated by peers in the field may be biased.
How the Task Force works
This current iteration of the Task Force was established to advise family physicians and other primary care providers on delivering preventive health care. These health-care professionals therefore comprise the majority of members, and all members have expertise in methods for evaluating health-care interventions, especially screening. They are unpaid volunteers, with a salaried civil service secretariat; systematic reviews of evidence are performed by contracted organizations. The Task Force methods for analyzing data are available on the website and are based on current best methods to define the questions, search for evidence, collate the evidence, then use the evidence to reach a recommendation. The evidence collation relies mainly on randomized controlled trials (RCTs) since these are the best methods of evaluating the efficacy of interventions. However, other evidence is also used where appropriate. At each step, outside experts are invited to review and comment, but do not vote on the actual recommendations.
Task Force decisions rely on published evidence so will always lag behind the latest innovations, but that is usually good. It takes time to fully evaluate new ideas; many are rejected for not living up to early promise, causing extra harms, or increasing costs excessively. Others may need adaptation or new learning before widespread use.
The Task Force considers the benefits, harms and costs of interventions when drafting a recommendation for clinicians. When trying to find early cases of disease, whether through a blood test, an X-ray or a screening questionnaire, the test/instrument used must be highly sensitive, picking up many minor variations from normal. Many of these slight variations are unimportant and will revert to normal if left alone or may persist but never develop enough to cause problems. If found by screening, such variations may lead to a cascade of further activities to determine whether this is or could become a serious disease. This process may include invasive testing and can lead to unnecessary treatments – even operations – and anxiety. People may suspend or alter their normal lives while going through these processes. Thus, more is not necessarily better, and patient outcomes may be worse with more “care.” In addition, patients may be rejected for life insurance – for income assurance, for their mortgage, or for travel.
Task Force decisions rely on published evidence so will always lag behind the latest innovations, but that is usually good.
It is inappropriate to inflict such harms on people unless the potential benefit outweighs those harms. Therefore, the Task Force must try to assess and balance the harms of any intervention (often immediate and to many) against the benefits that often accrue to few people and in the distant future.
Furthermore, the Task Force recognizes that its recommendations largely must be undertaken by family physicians who are already overloaded by simply trying to deal with the sickness that patients bring through their doors.
How much benefit from screening?
Many advocates of screening make the logical leap that if a disease has been discovered, it will lead to cure and a “normal” life. For most programs, the reality is that only a proportion of disease found is helped by early detection: much disease will proceed regardless, while even those helped may be left with scarring and after-effects and require long-term follow up. On the other hand, without screening, when disease is detected after symptoms appear, a proportion would still be cured. The absolute numbers suggest the benefits of screening are usually marginal.
When the preventable proportion of disease is higher, the benefits of screening can be greater than the harms. If the target population is expanded to lower risk groups, – for example younger people with low incidence of disease – the probability of benefit will be lower, but for most screening tests the harms remain similar, meaning the harms outweigh the benefits. Thus, choices of who to screen should not be based on finding every case, but on when this balance is likely beneficial.
The role of experts
During the process of preparing its guidelines, the Task Force requests experts in the field to participate in topic specific working groups as well as in discussions about evidence and reviewing draft guidelines. Most times, experts provide useful input and critiques that are incorporated into the guideline. But opinions unsubstantiated by evidence are disregarded.
An example of the opposition of experts came after the Task Force 2013 recommendations on cervical cancer screening (which was led by one of the authors of this article). In the 2000s, in Canada, most provinces recommended that women be screened annually, often including uncomfortable manual pelvic examinations, from about age 18, as did the United States. Many other countries initiated screening at later ages – 25 or even 30 years – and screened much less often. Yet, they did not have higher cancer rates. We found that in Canada, even before screening, invasive cancer before the age of 30 was rare, and especially before the age of 25. Based on that evidence, our working group recommended strongly against routine screening for women below age 20, weakly against for those under 25, weakly in favour for those 25 to 29 years, and strongly in favour for those over 30 years, with intervals of three years.
The response was vehement opposition from many gynecologists and advocacy groups. They opposed both raising the age for starting screening and longer intervals, as well as the cessation of “routine” pelvic examination. Provincial guidelines, which are mostly influenced by “experts” in the disease (but not experts in primary care, epidemiology or evidence), generally ignored the Task Force and continued recommending early and frequent screening. Change occurred slowly, with Alberta and British Columbia leading the way. Only now, more than 10 years later, have most provinces made those changes. Meanwhile, many young women had unnecessary examinations, and many older women have had them too frequently. As a result, many have been unnecessarily harmed by having multiple intrusive tests and invasive procedures for positive test results that led to further action. Some may have experienced pregnancy loss after surgery of the cervix to remove minor abnormalities found on Pap testing.
One of the experts asserted that the Task Force should have changed to HPV tests in 2013. Unfortunately, at that time, the evidence was limited, and the balance of benefits and harms was not yet clear. The cost was high, and the infrastructure was not yet available in Canada. Fortunately, change is occurring. HPV samples that can be taken by the women themselves are now replacing Pap tests in many provinces with research supporting longer intervals between tests. More than 10 years later, evidence to address these gaps is much improved and the Task Force is currently updating this guideline.
The Task Force reassesses its guidelines as new evidence emerges but is only funded to review and publish up to three guidelines per year. Thus, priorities must be set.
The future challenge
One of the benefits of any systematic review of evidence is to demonstrate the gaps in knowledge and what research is needed to address these gaps. The challenge to those who do not like Task Force recommendations is this: Can you provide or research the new evidence required to show how a different policy is better? Selectively picking and choosing evidence is inappropriate to provide sound and effective policy. If “experts” spent as much time and effort in improving the quality of their services and testing additional screening options, there could be real advances in the health of the public.
Canadians developed the concept of evidence-based medicine, and the first iteration of the Task Force was a pioneer in furthering these methods. Canadians continue to be leaders in developing more refined ways to assess evidence from more than just randomized controlled trials, and the current Task Force uses these methods.
The Task Force is focused on assisting the front line, where primary care clinicians must prioritize among the multitude of issues patients bring to the encounter. It would be a tragedy and disservice to all Canadians if lobbies for special interest groups were successful in disrupting this work.
Meantime, rather than pressing to over-screen those who already receive too much medicine, health-care professionals should be working to ensure recommended guidelines are applied for people who currently receive little or no primary care.
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Previously Published on healthydebate.ca with Creative Commons License
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