17.3 Public Health, Screening Principles, Health Inequalities & Health Promotion

Public Health, Screening Principles, Health Inequalities & Health Promotion

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Principles of Screening

Screening tests apparently healthy people to identify those at higher risk of a condition, so that earlier treatment improves outcomes. In the UK, the UK National Screening Committee (UK NSC) advises ministers on which programmes to introduce, using criteria developed from the Wilson and Jungner principles (1968):

1. The condition is an important health problem.
2. Its natural history is understood, with a recognisable latent or early symptomatic stage.
3. There is a suitable, acceptable test (safe, precise and valid).
4. There is an effective, accepted treatment, and earlier treatment gives better outcomes than later treatment.
5. Facilities for diagnosis and treatment are available, with an agreed policy on whom to treat.
6. The costs of case-finding are balanced against overall health spending, and case-finding is a continuing process.

Harms of screening include false positives (anxiety and unnecessary tests), false reassurance from false negatives, overdiagnosis and overtreatment of disease that would never have caused harm, and the biases discussed in section 17.2. People must be able to make an informed choice.

Current UK Screening (England)

• Antenatal and newborn: infectious diseases, sickle cell and thalassaemia, fetal anomaly and trisomies (section 9.5); newborn physical examination, blood spot and hearing screening (section 10.5).
• Adult: cervical (25–64), breast (50 to 71st birthday), bowel (50–74), AAA (men at 65), diabetic eye screening (people with diabetes aged 12 and over, annually or every 2 years if low risk) and targeted lung screening (section 13.5).
• The NHS Health Check (not a screening programme in the strict sense) offers adults aged 40–74 without known cardiovascular disease a check every 5 years, including QRISK cardiovascular risk assessment.

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Levels of Prevention

Population-wide strategies (for example reducing salt in processed food) can prevent more disease overall than targeting only high-risk individuals (the prevention paradox).

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Determinants of Health & Health Inequalities

• The Dahlgren and Whitehead "rainbow" model places individual factors (age, sex, genes) within layers of lifestyle, social networks, living and working conditions (housing, education, employment, healthcare) and wider socioeconomic, cultural and environmental conditions.
• Health inequalities are avoidable, unfair differences in health between groups. In England, people in the most deprived areas live shorter lives and spend more years in poor health; the Marmot Review (2010) showed a social gradient, with health worsening at each step down the social ladder.
• The inverse care law (Julian Tudor Hart, 1971): the availability of good medical care tends to vary inversely with the need for it.
• NHS England's Core20PLUS5 approach targets the most deprived 20% of the population, locally identified "PLUS" groups (for example ethnic minority communities, people experiencing homelessness, inclusion health groups) and five clinical areas (maternity, severe mental illness, chronic respiratory disease, early cancer diagnosis and hypertension case-finding).
• Doctors reduce inequalities by making services accessible (interpreters, reasonable adjustments, flexible appointments), avoiding assumptions, and recording and acting on social needs (for example social prescribing link workers).

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Health Promotion & Behaviour Change

• Making Every Contact Count (MECC): use routine contacts to give brief advice on smoking, alcohol, weight and activity.
• Stages of change (Prochaska and DiClemente): precontemplation, contemplation, preparation, action, maintenance and relapse; motivational interviewing helps people resolve ambivalence.

Smoking

• Very brief advice: Ask about smoking, Advise that the best way to stop is with support and medication, Act by offering referral to a stop smoking service and treatment.
• Effective aids (NICE NG209): combination nicotine replacement therapy (a patch plus a short-acting product), varenicline, and nicotine-containing e-cigarettes as a quitting aid, ideally with behavioural support. Stopping smoking at any age improves health.

Alcohol

• The UK Chief Medical Officers' low-risk guideline: no more than 14 units a week, spread over 3 or more days, with several alcohol-free days; no level is completely safe, and no alcohol is safest in pregnancy.
• Units = volume (mL) x ABV (%) / 1,000. A 750 mL bottle of 13% wine contains about 9.75 units.
• Screen with AUDIT-C (then full AUDIT); offer brief intervention; refer dependent drinkers for specialist treatment and manage withdrawal safely (section 8.3).

Weight & Physical Activity

• BMI categories: healthy 18.5–24.9, overweight 25–29.9, obesity 30 or more (kg/m²). NICE uses lower thresholds (overweight from 23, obesity from 27.5) for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background because of higher cardiometabolic risk at lower BMIs. A waist-to-height ratio of 0.5 or more indicates increased central adiposity risk.
• Management: multicomponent lifestyle programmes; medicines such as GLP-1 receptor agonists or tirzepatide within NICE-approved specialist services; bariatric surgery assessment for people with a BMI of 40 or more, or 35 or more with significant comorbidity such as type 2 diabetes.
• Physical activity (UK CMOs): adults should aim for at least 150 minutes of moderate or 75 minutes of vigorous activity a week, plus muscle-strengthening activity on 2 or more days, and reduce sitting time.

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Health Protection & Work

• Health protection is led by UKHSA and local authorities: outbreak control, notifiable diseases (section 16.2), vaccination programmes and environmental hazards. Herd immunity protects people who cannot be vaccinated when coverage exceeds the threshold for that infection (for example about 95% for measles).
• Fitness for work: people can self-certify for the first 7 days of sickness absence. After that a fit note is needed, which since 2022 can be issued by doctors and certain other registered professionals (nurses, pharmacists, occupational therapists and physiotherapists). Fit notes can recommend adjustments ("may be fit for work").
• Health economics: NICE appraises cost-effectiveness using the cost per quality-adjusted life year (QALY), which combines length and quality of life.