Primary versus secondary prevention and screening
Prevention is described in levels by when it acts: primary stops disease starting, secondary finds it early, and tertiary limits the harm of disease that is already established.
Remember
Screening people without symptoms is secondary prevention, because it finds disease early; primary prevention is the level that stops disease starting.
Prevention is described in levels, according to when in the course of a disease it acts.
Primary prevention stops disease from happening in the first place, for example through vaccination or health education. Helping adults stop smoking before they have developed disease is also primary prevention, because it lowers incidence (the number of new cases).
Secondary prevention catches disease in its early stages, often before it causes symptoms, so that treatment can begin sooner. Screening is the classic example. It means testing people who feel well and have no symptoms, in order to find disease early. In bowel cancer screening, people are sent a home kit that checks a small stool (poo) sample for blood.
Here is the exam trap. Bowel cancer screening does not stop the cancer from forming, so it is not primary prevention. When it finds a cancer, it finds it sooner than it otherwise would, so treatment can begin earlier and outcomes improve. That is early detection, which makes it secondary prevention.
Tertiary prevention is active treatment and rehabilitation of disease that is already established, to limit the negative consequences. Insulin therapy in type 2 diabetes is one example.
Two further levels are also described. Primordial prevention tackles the social causes of risk factors, and quaternary prevention protects patients from unnecessary medical interventions.
Place the activity on a timeline: primary is before disease, secondary is early, and tertiary is established disease.
Key facts
- Primary prevention
- stops disease from happening, for example by vaccination or health education.
- Secondary prevention
- finds disease early, often before symptoms, so treatment can begin sooner.
- Screening
- tests people without symptoms to look for early disease, so it is secondary prevention.
- Tertiary prevention
- gives active treatment and rehabilitation for established disease to limit its negative consequences, such as insulin therapy in type 2 diabetes.
- Screening result
- is not a diagnosis, because a positive result leads on to further tests, and a negative result does not always mean there is no cancer.
- Further levels
- primordial prevention aims to stop risk factors appearing at all, and quaternary prevention protects patients from unnecessary medical interventions.
Exam traps
- Bowel cancer screening is not primary prevention, because the test does not remove the causes of the cancer.
- Screening is not quaternary prevention, because an invitation to screening is designed to find disease early, not to limit medical activity.
- Detecting early complications in someone with established disease is tertiary prevention, because secondary prevention detects the initial disease itself.
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