Advantages and disadvantages of screening tests

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This information offers a detailed description of the advantages and disadvantages of . It also explains why research is needed to be able to say which tests are beneficial and which are harmful.

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 are designed to detect diseases as early as possible so that they can be treated effectively or, ideally, cured. The idea makes perfect sense on the face of it. Certain tests, like colonoscopies, can also detect cancer in its earliest stages, enabling it to be removed. Screening tests that stop a disease from developing are called “preventive testing.”

But doesn‘t always stop disease. One example of this is for ovarian cancer. This often involves an ultrasound scan, which doesn’t improve the person‘s chances of recovery. Screening for other diseases, such as prostate cancer, does have advantages but there are serious disadvantages too.

A few simple questions can help you work out which tests you want and which ones you don‘t think you need. This information offers a detailed description of the advantages and disadvantages of . It also explains why research is needed to be able to say which tests are beneficial and which are harmful.

What are the potential advantages of screening?

A lot of research has been done on a number of tests and they were found to have the following potential advantages:

  • They can prevent a disease (preventive testing): This is true of bowel or cervical cancer screening, which look for benign (non-cancerous) early signs of cancer. If it finds any and they’re remedied, the cancer can be prevented. So the means you don‘t suffer the mental stress of being diagnosed with cancer and you don‘t receive treatment that can sometimes have severe side effects.
  • Although the tests can‘t prevent the disease, they can improve your chances of only needing low-impact treatment and of recovering. One example is breast cancer screening, which can detect breast cancer before it spreads to other parts of the body.

But even well-studied methods aren‘t perfect. For instance, they usually reduce a person‘s risk of dying of cancer by 30% to 60% but they don’t eliminate it completely.

What are the potential disadvantages of screening?

Like a drug, has numerous possible side effects. But it‘s important to know about the potential disadvantages in order to make the right decision for you. It can also help you cope better with any disadvantages that affect you.

The disadvantages can be split into the following categories:

  1. The test can have side effects or cause complications like injuries.
  2. The test delivers an incorrect abnormal result (false positive result). This can cause unnecessary worry and stress.
  3. The test detects the disease but the person’s chance of recovery doesn’t improve as a result.
  4. There hasn’t been much research on the method concerned so it’s not clear whether it offers any advantages and whether they outweigh the potential disadvantages.

The following sections explain the disadvantages in these categories in more detail.

What are the potential side effects and complications?

The potential side effects and complications depend on the test method used. Taking blood for a blood test can cause bruising, for instance. And a colonoscopy can cause injury to the colon (though this is rare).

In Germany, programs are only allowed to use x-rays and (CT) scans if they‘ve been authorized by the Federal Office for Radiation Protection (Bundesamt für Strahlenschutz) because they pose a small risk of cancer. Currently, the only authorized test is the mammography examination used in breast cancer .

What is a “false positive” test result?

The word “” comes from the technical term for sifting or sieving. The idea is to “sift” through a large group of people with no symptoms to find the ones that do have the disease.

That can be quite difficult because diseases like cancer are – thankfully – not that common. Experts on the program for breast cancer, for example, assume that around 8 out of 1,000 women aged 50 or over have the disease without knowing it.

So the aim of the is to:

  • correctly identify people who do have the disease and
  • correctly identify people who do not have the disease.

But, in reality, there are two types of mistake that can happen:

  • The misses someone who does have the disease. The medical term for this is a “false negative result.”
  • Sometimes the result is abnormal although the person doesn’t actually have the disease. This is referred to as a “false positive result.”

To rule out false positive results, the usually has two parts. The first one checks for abnormalities or signs of the disease in question. If it finds anything, a second part is carried out to determine whether the person does actually have the disease. An example would be a mammography examination that finds signs of breast cancer. This would be followed up by a biopsy, which is the only way to find out whether it is actually cancer.

The fact that tests can produce false-negative results means it‘s particularly important to take seriously any symptoms that could be a sign of a disease – even if you‘ve only just been for .

Important:

A positive result is not a . Most abnormal results turn out to be wrong (false) when more tests are done.

Does screening improve your chance of recovery?

Getting a positive test result and a confirmed can be quite perplexing. A is always bad news – especially if it‘s cancer. On the other hand, providing a is precisely the point of – it‘s meant to detect diseases earlier in order to improve the chance of recovery.

But cancers behave in different ways so early detection doesn‘t necessarily mean more effective treatment or, in an ideal scenario, complete recovery.

The aim of cancer is to identify tumors before they spread to other parts of the body (metastasis). If they do spread, it‘s very difficult to treat them and the chances of recovery are lower. But there are four different types of tumor, and is only really of benefit for the first one:

  • Screening can improve a person‘s chance of recovery if the tumor is one that only grows in one place (locally) for a relatively long time (first type). A test during that time can detect the tumor and then it can be successfully treated.
  • The second type of tumors, on the other hand, spread at an early stage (metastasis). Often, does not find them in time. This means that the is made earlier but the chance of recovery doesn‘t improve. In other words, having a test doesn’t mean the person lives longer. They just learn that they have cancer earlier.
  • Some tumors don’t spread at all or not until much later, which means they can still be successfully treated even if the person already has noticeable symptoms (third type). So doesn‘t affect the chance of recovery in these cases either.
  • Some types of tumor grow so slowly that there are never any noticeable symptoms (fourth type). When detects this type of tumor, the result is what‘s known as “overdiagnosis” – a that wouldn‘t have any impact on the person‘s health.

The problem is that when a tumor is found it‘s usually not possible to say for definite in advance what type it is or how common each type is. For instance, experts assume that half of the prostate tumors detected by would never be noticed if wasn‘t carried out.

Is good-quality research available on the effects of screening?

Good-quality research on is necessary to assess the advantages and disadvantages. Research has been done on most of the tests that public health insurance covers.

Research on the advantages and disadvantages of isn‘t only about the accuracy of tests. The most important question is whether they have any health benefits for the people who go for .

The benefits and harmful effects of can only be weighed through comparative studies. They entail one group having regular tests, while the other group does not. At the end of a study, the researchers look to see if, for example, less people in the first group died of the disease or whether caused more complications than in the other group.

Randomized controlled studies, in which the participants are randomly assigned to a specific group, deliver the best results. Studies of this type have been conducted for numerous tests, like mammography and colonoscopy examinations.

In Germany, some tests are offered as what are called individual health care services (in German: Individuelle Gesundheitsleistungen, or IGeL for short). These are usually services for which no good-quality research is available on the benefits and harmful effects of testing or for which good-quality studies haven’t found any advantages. They include ultrasound examinations used in ovarian cancer screening, for example. You have to pay for these tests yourself. The public health insurance funds provide information (in German) about certain IGeL services on the website of the Medical Review Board of the Statutory Health Insurance Funds (Medizinischer Dienst des Spitzenverbands der Krankenkassen, MDS).

What are the good practice requirements for screening programs?

As early as the 1960s, the Word Health Organization (WHO) drew up good practice requirements for programs in response to the disadvantages described above. The WHO criteria include the following:

  • Screening should be done only for diseases with serious consequences, so that tests can potentially have clear benefits to people’s health.
  • The test must be reliable enough, and not harmful in itself.
  • There must be an effective treatment for the disease when detected at an early stage – and there has to be scientific proof that that treatment is more effective when started before symptoms arise.
  • Neutral information should be made available to the public, to help people decide for themselves whether or not to have a test.

The WHO points out that detecting a disease early does not automatically have a benefit. If an early followed by treatment doesn’t result in a better outcome than a late , the early merely extends the person’s anxiety – unnecessarily because they don’t benefit from earlier treatment anyway.

Gemeinsamer Bundesausschuss (G-BA). Früherkennung von Krankheiten. 2021.

Giersiepen K, Hense HW, Klug SJ et al. Entwicklung, Durchführung und Evaluation von Programmen zur Krebsfrüherkennung. Z Arztl Fortbild Qualitatssich 2007; 101(1): 43-49.

Kasper DL, Fauci AS, Hauser SL et al. Harrison's Principles of Internal Medicine. New York: McGraw-Hill; 2015.

Petticrew MP, Sowden AJ, Lister-Sharp D et al. False-negative results in screening programmes: systematic review of impact and implications. Health Technol Assess 2000; 4(5): 1-120.

UK National Screening Committee (NHS). Criteria for appraising the viability, effectiveness and appropriateness of a screening programme. 2015.

Wilson JM, Jungner G. Principles and practice of screening for disease. (Public Health Papers; No. 34). J R Coll Gen Pract 1968; 16(4): 318.

World Health Organization (WHO). Screening programmes: a short guide. Increase effectiveness, maximize benefits and minimize harm. 2020.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Created on January 22, 2025

Next planned update: 2028

Publisher:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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