Community medicine chapters
Levels of prevention
The four levels of prevention (primordial, primary, secondary and tertiary), the modes of intervention at each level, and how to classify any preventive measure, with examples from Pakistan.
- Primordial prevention stops risk factors arising in the first place; primary prevention stops disease starting (health promotion and specific protection such as vaccines).
- Secondary prevention finds disease early and treats it (screening, early diagnosis); tertiary prevention limits disability and rehabilitates.
- The five modes of intervention: health promotion, specific protection, early diagnosis and treatment, disability limitation, rehabilitation.
On this page
Overview
Prevention means stopping disease, or its harms, at any stage of its natural history. Park describes four levels of prevention linked to five modes of intervention.
The levels of prevention
| Level | When it acts | Aim | Modes of intervention |
|---|---|---|---|
| Primordial | Before risk factors appear | Stop risk factors developing in the population | Health education, healthy lifestyles, social and economic policy |
| Primary | Before disease starts (pre-pathogenesis) | Stop the disease occurring | Health promotion, specific protection |
| Secondary | Early disease (early pathogenesis) | Detect and treat early; halt progress; reduce spread | Early diagnosis and treatment (including screening) |
| Tertiary | Established disease (late pathogenesis) | Reduce disability and complications | Disability limitation, rehabilitation |
Primordial prevention
Prevents the emergence of risk factors in a population, especially in children. Example: encouraging healthy eating, physical activity and not starting smoking, so that hypertension, obesity and diabetes do not develop.
Primordial prevention targets the risk factors, not the disease; it is most useful for chronic diseases and works mainly through health education of the young.
Primary prevention
Acts before the disease begins.
Health promotion (general, not disease-specific):
- Health education.
- Good nutrition.
- Clean water and sanitation; housing.
- Lifestyle changes.
Specific protection (aimed at one disease):
- Immunisation (BCG, polio, measles and other vaccines in the national programme).
- Chemoprophylaxis (for example antimalarials for travellers).
- Micronutrient supplements (iron and folic acid, iodised salt, vitamin A).
- Protection from occupational hazards; road safety measures; mosquito nets.
Primary prevention can use a population (mass) strategy, which shifts the whole population's risk (for example less salt in food), or a high-risk strategy, which targets those at high risk (for example people with a family history).
Secondary prevention
Early diagnosis and adequate treatment: detecting disease at an early, often symptom-free stage and treating it to stop progress and spread.
- Screening: Pap smears for cervical cancer, blood pressure checks, blood glucose testing in high-risk adults, mammography.
- Case finding and treatment of infectious diseases (for example TB treatment, which also protects the community).
Screening is secondary prevention: the disease has already started, even if there are no symptoms.
Tertiary prevention
Used when the disease is established, to limit disability and restore function.
- Disability limitation: treatment to prevent complications (for example good diabetes control to prevent foot ulcers; treating leprosy to prevent deformity).
- Rehabilitation: medical (physiotherapy after a stroke), vocational (training for new work), social and psychological.
Quaternary prevention
Protecting patients from unnecessary or harmful medical tests and treatment (over-medicalisation). It is a newer term and is mentioned in some books.
How to classify a measure
Ask: has the disease (or the risk factor) already started?
| Measure | Level |
|---|---|
| Teaching schoolchildren not to start smoking | Primordial |
| Health education on hand washing | Primary (health promotion) |
| Measles vaccination | Primary (specific protection) |
| Iodised salt to prevent goitre | Primary (specific protection) |
| Pap smear screening | Secondary |
| Blood pressure screening in adults | Secondary |
| Treating a sputum-positive TB patient | Secondary |
| Physiotherapy after a stroke | Tertiary (rehabilitation) |
| Foot care for a diabetic with neuropathy | Tertiary (disability limitation) |
| Artificial limb after amputation | Tertiary (rehabilitation) |
Immunisation is specific protection (primary), not health promotion. Health education in general is health promotion.
Treating a case of an infectious disease is secondary prevention for that patient but acts as primary prevention for the people it would otherwise infect.
Most questions give a measure and ask its level. Know the four levels, the five modes of intervention, that screening is secondary, that immunisation and chemoprophylaxis are specific protection, that rehabilitation is tertiary, and what primordial prevention means.
Quick revision
- Primordial: prevent risk factors (lifestyle in children).
- Primary: health promotion + specific protection (vaccines, chemoprophylaxis, iodised salt).
- Secondary: early diagnosis and treatment, screening.
- Tertiary: disability limitation and rehabilitation.
- Quaternary: avoid over-medicalisation.
Written by The House Job from Excel Community Medicine and Park's Textbook of Preventive and Social Medicine (named in the UHS PGET syllabus).
FAQ
What is primordial prevention?
Preventing risk factors from developing in a population, for example by promoting healthy lifestyles in children.
Is screening primary or secondary prevention?
Secondary prevention, because it detects disease that has already begun.
What are the modes of intervention in primary prevention?
Health promotion and specific protection.
What does tertiary prevention include?
Disability limitation and rehabilitation.