Levels of prevention
- Concept
Prevention acts before risk appears, before disease, before symptoms, after harm, and also against too much medicine.
What it is
The levels of prevention sort interventions by the point in natural history where they act. Primordial prevention stops risk factors from appearing; primary stops disease from starting; secondary finds and treats it early; tertiary limits its sequelae; quaternary protects the patient from unnecessary interventions. A classic exam question: name the level from an example.
Worked example
- Data (made up): a municipality has 50 000 adults and plans a programme against type 2 diabetes.
- Primordial: a local bylaw creates cycle lanes and school areas free of sugary drinks for all 50 000.
- Primary: 8 000 adults with prediabetes join a diet and exercise programme so they do not progress to diabetes.
- Secondary: blood glucose is measured in 12 000 adults over 40; 600 have undiagnosed diabetes: 600 / 12 000 = 5 %.
- Tertiary: 2 500 people with known diabetes join foot care; amputations fall from 20 to 12 a year.
- Reduction: (20 − 12) / 20 = 0.40, that is, 40 % fewer amputations.
- Quaternary: 300 healthy people who asked for tests every few months stop receiving tests without an indication.
- Reading: one problem has one intervention per level; each targets a different group and is measured with its own number.
The five levels with one example each
| Level | When it acts | Example |
|---|---|---|
| Primordial | Before the risk factor exists | Public spaces for exercise, food labelling |
| Primary | Healthy person, before disease | HPV vaccine, wearing a helmet |
| Secondary | Subclinical disease | Cervical cytology or HPV testing, blood pressure checks |
| Tertiary | Established clinical disease | Cardiac rehabilitation, diabetic foot care |
| Quaternary | Person exposed to over-intervention | Not repeating imaging without an indication in a healthy patient |
Markers
- Primordial
- Primary
- Secondary
- Tertiary
- Quaternary
In practice
- In an exam question, first decide whether the person is healthy, ill without symptoms or ill with symptoms: that sets the level.
- Quaternary prevention is part of daily work: every test without an indication brings false positives, costs and anxiety.
Common pitfalls
- Calling screening primary: screening looks for disease that already exists, so it is secondary.
- Mixing up primordial and primary: primordial prevents the risk factor; primary acts when the risk already exists.
Test yourself
Think of the answer, then tap the question to see it.
Which level of prevention is cervical cancer screening with cytology?
Secondary prevention: it finds lesions that already exist, before symptoms, so they can be treated early.
Which level is HPV vaccination of healthy girls?
Primary prevention: it stops the infection and the disease from starting.
What does quaternary prevention aim to do?
Protect patients from overmedicalisation: unnecessary tests or treatments that may harm more than they help.
How do primordial and primary prevention differ?
Primordial prevention stops risk factors from appearing in the population; primary prevention acts on people already exposed to risk so they do not become ill.
Connections
Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.
Sources: Principles of Epidemiology | Lesson 1 - Section 9 (Centers for Disease Control and Prevention, 2012); Screening programmes: a short guide. Increase effectiveness, maximize benefits and minimize harm (World Health Organization, Regional Office for Europe, 2020).
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Representative model, for educational purposes only.