Why is Overdiagnosis an issue?
Underdiagnosis is self-evidently a problem when it occurs.
Overdiagnosis is no less important. Since this page was originally published in 2014 following a lot of debate in The US and UK, the issue is being increasingly recognised in Australia. The National Prescribing Service’s independent “Australian Prescriber” lead with an editorial called “Caution! Diagnosis Creep” in 2016.
It seems sometimes as though there is a potent mix of the following ingredients mixed together to form an powerful force.
- Tests are becoming increasingly sensitive to the extent that modern tests often pick up abnormalities that are not clinically significant …. however, in order to establish that the abnormality is not significant, other tests are often required
- More tests are being done than ever before. stutine blood tests increase in both quantity and sensitivity over time.
- Tests are abnormal when the result lies outside what is normal for that test – and normal is defined as a particular percentage of the population. When a 95% threshold is used (for example), there will be at least one abnormal test for every 20 tests performed – and the average blood tests report on far more than 20 tests.
- The threshold (or bar) for making diagnoses are becomingly lower over time. Criteria for making diagnoses change all the time, and usually this results in more people with the diagnosis rather than fewer … the aim is for those people to be eligible for treatment that improves the symptoms or outcome but this often is not the case
- Single Disease groups (both patient and professional) focus only on that disease or group of diseases. The greater the number of cases (prevalence) then the better the group can fight for limited resources
- Doctors do not want to “miss” a diagnosis or do not want to appear to have missed a diagnosis (even if the test result and the symptoms are not related).
- Doctors are expected to give a diagnosis & may prefer to explain patient’s symptoms in terms of a single diagnostic label. Symptoms (and life) are often not so simple.
- The idea of screening for disease (picking up disease before it causes symptoms) is appealing. We’d all like to know that we have cancer before we develop symptoms from that cancer. The problem is that cancer is not black-and-white and many cancers are in fact harmless. When cancer is searched for hard enough in older people it is often found eg. prostate cancer test. The difficulty is that current methods cannot distinguish between cancers that would never cause a problem and cancers that are aggressive. There are effective screening programmes, of course, such as bowel, breast and cervical cancer screening programmes. However, these screening programmes are the exception rather than the rule. Screening programmes have an important role to play to reduce health for populations but are well documented to have adverse consequences as well.
- Diagnostic labels are often frightening to people and the very label can convert people without symptoms to patients with symptoms who need medical attention.
Examples of the problems of overidagnosis are numerous. Take one example, so-called Grade 1 hypertension. This refers to mildly raised Blood Pressure (140-159/90-99) . A recent Cochrane review summarised what is already known: That treating people with grade 1 hypertension with medication (who do not have other risk factors) does not reduce their risk of stroke or heart attack. Research has shown that the very diagnostic label of “hypertension” causes harm to a number of people who consider themselves thereafter to be ill.
Risk of overdiagnosis cover all medical and surgical specialities. Wherever you go looking there are numerous examples.
Pointless diagnostic labels are abundant and is particularly concerning in children’s health. It sometimes seems as though “every” infant has “GORD” (Gastro-oeophageal Reflux Disease). Around a quarter of babies have reflux which is caused by an immature sphincter muscle at the bottom of the oesophagus. This is a normal part of being a baby. Being told that the baby has a “disease” called “GORD” may cause unecessary alarm. Sure, some babies do have GORD, and this is important to pickup, but most babies with reflux do not have GORD. So let’s get the label right and call reflux just that, and GORD when there are documented medical complications or particularly severe symptoms.
A strong example (among many) comes from a national screening program for thyroid cancer introduced in South Korea. Adults were offered ultrasound of the thyroid gland. Guess what? After the program was introduced, thyroid cancer became the most commonly diagnosed cancer. The program kept the pathologists and surgeons busy, yet the number of people dying from thyroid cancer did not change significantly. Why can this be? Because lots of people have a harmless type of thyroid cancer, and there’s no point in diagnosing something that is not harmful to health.
There have been huge improvements in medical care over the last few years. However, the tools used are becoming increasingly sensitive – which is great for sorting out conditions where early diagnosis is important (eg. lung cancer) but not so great when someone who is not at increased risk is labelled with something that is harmless and causes anxiety.
The issue of making appropriate diagnoses and avoiding over-diagnosis is tricky terrain for patients and The GP, and it’s too easy to slip into labelling for the sake of it without thinking through the pros and cons. Of course, medical advances have contributed enormously to improved outcomes through earlier diagnosis and better treatment, but the story isn’t as simple as that.
It’s usually much harder to de-label than to label in the first place.
Be aware that asking for a test and often does have negative outcomes