Treatments and diagnostic tests

Screening – what might help you decide

Medical tests are usually done to find out what is causing certain symptoms. Screening tests are different: they are done in people without any symptoms. They aim to detect diseases at an early stage, before any symptoms become noticeable. In many cases that can, but does not always, have advantages.

Detecting a disease at an early stage is only a desirable goal if treatment is then more successful. In other words, early treatment has to benefit people’s health. But, as with any medical intervention, screening tests sometimes do not have any benefits, or might even have harmful effects.

Some screening tests have more advantages than disadvantages, others do more harm than good, and some are still a subject of controversy.
So it is worth weighing up the pros and cons of a screening test before deciding whether or not to have it.

Criteria for assessing screening tests

The World Health Organization (WHO) has defined criteria for evaluating screening tests, which may help you decide whether or not to have a particular test. The WHO criteria include the following:

  • Screening should be done only for diseases with serious consequences, so that screening tests have clear benefits to people’s health.
  • The screening test must be reliable enough, and not harmful in itself.
  • There has to be an effective treatment that works better when started at an early stage – in other words, before symptoms arise and you would have gone to the doctor anyway.
  • Neutral information should be made available to the public, so people can weigh up the pros and cons for themselves.

Most screening tests cannot prevent diseases

The aim of screening is to detect diseases before symptoms arise. Some screening tests also look for abnormal changes that could later develop into a disease. If found, abnormal changes are treated. But the screening test does not influence whether or not a disease develops or any abnormal changes occur.

Abnormal changes do not always develop into a disease

A lot of people have treatment as a result of screening tests, although they would never have gotten the disease. This is because many abnormal changes do not necessarily develop into a more serious condition, or might even go back to normal again by themselves, without causing any health problems.

No medical test is perfect

The medical tests that are used for screening often do not deliver a definite diagnosis. They often just look to see if anything is abnormal, and then further tests have to be done to find out more.

In a lot of cases the abnormal test results turn out to be a false alarm. This can make people worry for no reason, and means that they sometimes have further tests that would not have been necessary.

Sometimes a screening test does not detect anything abnormal in people who are actually ill. In other words, it fails to detect a disease. Or the results might not be clear; they sometimes lie in a gray area between normal and abnormal results.

Screening does not offer any guarantees

If you have worrying symptoms, it is important to take them seriously and have them checked out by a doctor – even if the results of your last screening test were okay.

Questions to ask your doctor

If you are finding it hard to decide whether or not to have a screening test, it might help to talk to a doctor. Here are a few questions you could ask:

  • How likely am I to get this disease at my age?
  • Would detecting the disease early benefit my health in the long term? For instance, is there any scientific proof that it might help me live longer?
  • What adverse effects might be associated with the screening test, with possible tests following screening, and with the treatment? How common are they?
  • How often, and at what intervals, will I have to have a screening test in order to be able to benefit from screening?
  • How often does the test lead to false alarms, and how often does it fail to detect a disease?

Do not worry too much about things that might never happen

A wide range of screening tests are available nowadays. Some are considered to be worthwhile. Others have not yet been well researched or do not have an overall benefit, but are still offered and sometimes even strongly promoted. That might give people the impression that there are diseases lurking around every corner, and that you can protect yourself from them.

But in most cases the risk of getting one of the diseases that can be screened for is not particularly high. And even the best screening tests cannot guarantee your health. We all have to live with the fact that we might get ill. So it is best not to worry too much or drive yourself crazy thinking about diseases that you do not have, and probably never will.