In recent years, doctors and academics have become more and more interested in a problem referred to as ‘overdiagnosis’. There are several ways that overdiagnosis can be defined.
One particularly useful way is to think of it as the diagnosis of a disease that would never have caused a person symptoms or led to their death, whether or not it had been found through a medical test. In other words, even if a person had not had the test, the disease would never have caused them any harm.
Catching it early
It may not be obvious how this can happen. As an example, imagine a woman going for breast screening, which tries to find cancer at an early stage, before it starts causing symptoms.
The thinking behind this type of test is that if the disease is found early, it will be easier to treat and there is a higher chance of curing it. Most people are familiar with this idea that ‘catching it early’ is a good thing.
The cancer is real but the diagnosis does not benefit the woman at all; it results in treatment that she did not need (‘overtreatment’).
So, suppose a woman who has no symptoms goes for screening and the test finds cancer: she would usually go on to have treatment (e.g. surgery).
However, although she has no way of knowing for sure, it is possible that the cancer was growing so slowly that she would have lived into old age and died of something unrelated, without ever knowing about the cancer, had she not gone for screening.
The cancer is real but the diagnosis does not benefit the woman at all; it results in treatment that she did not need (‘overtreatment’). In fact, if she had not had the screening test, she would have avoided all the problems that come with a cancer diagnosis and treatment.
What research has found
If you find the idea of overdiagnosis counter-intuitive, you are not alone. Several studies have tried to gauge public opinion on the issue and found that this is a fairly typical view, partly because the notion that some illnesses (like cancer) might never cause symptoms or death is one that does not receive much attention and is often at odds with our personal experiences.
Results from an Australian study in 2015 found that awareness of ‘overdiagnosis’ is low – in a study of 500 adults who were asked what they thought it meant, only four out of ten people gave a description of the term that was considered approximately correct and these descriptions were often inaccurate to varying degrees.
For example, people often thought in terms of a ‘false positive’ diagnosis (diagnosing someone with one illness when really they do not have that illness at all), or giving a person ‘too many’ diagnoses.
Is this the same in the UK?
We asked a group of 390 adults whether they had come across the term ‘overdiagnosis’ before and asked them to describe what they thought it meant
We wanted to find out whether this was also true in the UK. We asked a group of 390 adults whether they had come across the term ‘overdiagnosis’ before and asked them to describe what they thought it meant in their own words, as part of an online survey.
We found that only a minority (three out of ten people) had encountered the term and almost no-one (10 people out of all 390) described it in a way that we thought closely resembled the concept described above.
It was not always clear how best to summarize people’s descriptions but we found that people often stated that they had no knowledge or had similar conceptions to the Australian survey such as ‘false positives’ and ‘too many’ diagnoses.
Some descriptions were somewhat closer to the concept of overdiagnosis such as an ‘overly negative or complicated’ diagnosis (e.g. where the severity of an illness is overstated) but there were also some descriptions that we found more surprising such as being overly health-conscious (e.g. worrying too much about health issues).
Room for improvement
Many people who work in public health and healthcare believe that people should be aware of the possibility of overdiagnosis, particularly since they will eventually be offered screening tests in which there is this risk.
Our findings show that there is substantial room for improvement in how we inform the public about overdiagnosis.
In this respect, our findings show that there is substantial room for improvement in how we inform the public about overdiagnosis. In part, this may be due to the term itself not having an intuitive meaning, in which case other terms might be more helpful (for example the term ‘unnecessary detection’).
This could be tested in future studies. Our findings also motivated us to find out the extent to which trusted information sources (such as websites run by the NHS and leading health charities) are already providing information on overdiagnosis.
We would like to share the findings from this study in a follow-up blog post. We will be posting this on the UCL Health Behaviour Research Centre website soon
Do medical doctors understand that many of the assumptions when modelling harms in papers trying to measure the “impact” of overdiagnosis in cancer screening may be spurious?
An example is the use of all-cause mortality in an attempt to compare the effectiveness of screening, or lack thereof. Yet such studies usually lack the statistical power for all-cause mortality to be a meaningful measure of effectiveness. Hence any conclusions about over-diagnosis based on this measure are spurious. Both over and underdiagnosis are harmful and advocating policies to increase or decrease screening are social experiments with uncertain outcomes.
The second is assuming that cancer diagnosis is necessarily traumatic, or will lead to aggressive treatments like radiotherapy, chemotherapy or -ectomies. Earlier diagnosis means less aggressive treatment, to the point of avoiding chemotherapy or
The level of psychological trauma is determined by the medical community, who have long kindled a culture of fear around cancer. By all means try to destigmatise over-diagnosis, but understand that under-diagnosis is often just as common and arguably more harmful. I think it is just as valuable to attempt to destigmatise cancer diagnoses themselves.