Every general-practice consultation is an opportunity to go beyond the presenting complaint and address prevention, early detection, and health promotion. This lecture, delivered by Prof William CW Wong (Department of Family Medicine & Primary Care, HKU), anchors the Family Medicine clerkship by teaching you how to think about prevention systematically — from the population level down to the individual sitting in front of you — and illustrates it with a deep-dive into Hepatitis B as a model for cross-society health promotion. ^[1]

1. Session 1 — Preventive activities in Family Medicine: Recap the criteria and range of screening and understand what screening means for an individual person.
2. Session 2 — Health promotion in primary care: Understand health promotion activities specific to primary care (using Hepatitis B as an example), recognise difficulties in delivering health promotion, and learn ways to overcome them.

The historical US estimate shown in the lecture attributed about half of deaths to behavioural/external causes. ^[1]

Why this matters: The table is an older population-attributable estimate, not a current death-certificate count and not proof that every listed death is individually preventable. Its conceptual message is that tobacco, diet/activity and alcohol create a large preventable burden and are legitimate primary-care targets.

The lecture defines four levels of prevention mapped to the disease continuum. ^[1]

How to read the continuum diagram (slide 4): disease moves vertically from “normal/no problem” through a subclinical phase, symptoms, functional interference and complications. The bracket positions—not just the labels—carry the teaching: primary prevention acts before disease is established; secondary prevention occupies the detectable but asymptomatic window; ordinary reactive care begins once symptoms appear; tertiary prevention limits disability and complications after established disease. Quaternary prevention, introduced on the next slide, can apply at any point where medical activity itself risks harm.

Every general practice consultation has four domains beyond the presenting complaint. ^[1]

┌─────────────────────────────────────────┐
│         GP Consultation Potential        │
├───────────────────┬─────────────────────┤
│ Presenting        │ Continuing care      │
│ complaint         │ (chronic disease     │
│ (overt/covert)    │ management)          │
├───────────────────┼─────────────────────┤
│ Prevention,       │ Modification of      │
│ early detection,  │ abnormal help-       │
│ health promotion  │ seeking behaviour    │
├───────────────────┼─────────────────────┤
│ Coordination      │                     │
│ of care           │                     │
└───────────────────┴─────────────────────┘

Why this model matters: A patient comes in for a sore throat. You treat the sore throat (presenting complaint). But you also notice they smoke — so you give brief smoking cessation advice (prevention). You check if their BP has been measured recently (early detection). If they've been coming in frequently for trivial complaints, you explore why (modification of health-seeking behaviour). If they have diabetes being managed by a specialist, you ensure follow-up is coordinated (coordination of care). This "opportunistic" approach is the hallmark of comprehensive primary care.

Visual point from slide 7: the exploded five-slice pie shows five opportunities that coexist within one encounter—presenting complaint, continuing care, coordination, health-seeking behaviour and prevention/health promotion. The slice sizes are illustrative; they are not measured proportions of consultation time.

The lecture lists eight domains of individual preventive activities: ^[1]

1. Immunisation
2. Birth control
3. Sexually transmitted diseases
4. Mental health
5. Smoking
6. Alcohol
7. Screening
8. Dental care

Each of these represents a conversation you can have during any consultation. The key is being systematic and opportunistic — you don't wait for the patient to ask; you proactively screen and counsel.

The lecture lists the following childhood vaccines; this is a broad vaccine list, not the Hong Kong schedule:

National/local programmes differ: vaccines such as Hib, rotavirus and meningococcal vaccine may be recommended or privately available without being part of a particular year's universal Hong Kong programme. The current HK programme includes BCG and HBV from birth, DTaP-IPV and pneumococcal vaccination in infancy, MMR/varicella, and school-age boosters/HPV; use the live Department of Health schedule rather than inferring coverage from this broad slide list ^[13]. Also distinguish varicella vaccine in children from zoster vaccine for shingles, which is not the same childhood indication.

The lecture distils the 10 Wilson-Jungner criteria into 5 key points: ^[1]

Additional prompts from slide: RCT evidence; huge pressure to screen; ethical/legal issues. ^[1] These are not three extra Wilson-Jungner criteria. They remind you to ask whether screening improves patient-important outcomes—not merely detection—and whether consent, equity, false positives, overdiagnosis and downstream responsibility have been addressed.

Why each criterion matters from first principles:

• Long, detectable pre-clinical phase: Screening can only shift outcome if disease is detectable early enough for treatment to help. A short or poorly defined detectable phase makes an effective programme much harder; a long precursor phase, as in cervical neoplasia, is favourable.
• Treatment must improve outcome: If you can detect it early but there's no treatment that changes the natural history, you've just given the patient more years of anxiety (lead-time bias). This is the core argument against routine PSA screening.
• Suitable test: Sensitivity matters, but so do specificity, predictive values in the target population, reproducibility and an agreed confirmatory pathway. “Sort out false positives later” is not harmless—the downstream burden is part of programme evaluation.
• Acceptable to patient: A perfect test that nobody agrees to take is useless. This is why FIT (faecal immunochemical test) has replaced guaiac FOBT — it's easier, more acceptable, and more sensitive.
• Cost-effective and sustainable: Healthcare resources are finite. Screening must be compared against alternative uses of the same money and delivered as a continuing programme rather than a one-off campaign.

The full 10-point Wilson-Jungner criteria are also listed in senior notes and are frequently examined. ^[6][7]

Chronic illnesses in four domains:

1. Cardiovascular disease
2. Cancers
3. Degeneration
4. Disability of ageing

The lecture lists the following CV risk factors to screen for:

Connection to related material: The HK Consensus 2016 on primary CVD prevention recommends non-pharmacological measures (diet, moderate-intensity exercise ≥30 min × ≥5 days/week, weight loss, smoking cessation) alongside pharmacological optimisation (BP, glucose to HbA1c < 7%, LDL targets based on risk stratification). ^[8]

Lecture-Listed Screening (with Slide-Era Percentages)

Prof Wong uses Hepatitis B as a paradigm for cross-society health promotion because:

1. HBV has historically been highly prevalent in Hong Kong and China; the exact prevalence changes by year, age cohort and dataset.
2. Despite neonatal vaccination since 1988, there is a huge undiagnosed pool of adults infected before universal vaccination.
3. Effective treatment exists (nucleos(t)ide analogues) — meaning that finding cases saves lives.
4. It illustrates the full spectrum: primary prevention (vaccination), secondary prevention (screening), tertiary prevention (treatment to prevent cirrhosis/HCC), and quaternary prevention (avoiding unnecessary invasive procedures in low-risk carriers).

In Hong Kong, only 22% of HBV-infected individuals are diagnosed, and only 17% are treated. ^[1]

"Newborn vaccination and maternity testing alone is insufficient to eliminate HBV (requires 90% reduction in new chronic infections and 65% reduction in mortality). We need to find the missing patients!" ^[1]

Why this matters: Vaccination prevents new infections but does not find or treat people already chronically infected. The current WHO fact sheet estimates 240 million people living with chronic HBV in 2024; only 27% knew their status and 4.3% were receiving antiviral treatment. Those live figures supersede the lecture-era global totals but reinforce the same diagnosis-to-treatment gap ^[17].

The paired graphs run from 1990 to 2100 and compare a baseline with progressively stronger diagnosis, treatment and linkage scenarios. Birth vaccination/maternity testing sharply reduces new chronic infection, but mortality falls far less unless existing infections are found and treated. The curves therefore visualise a sequence:

Screening without linkage/treatment moves the diagnosis curve but cannot achieve the mortality target.

The lecture highlights WHO policy guidance for targeted HBV/HCV screening:

• Dialysis patients
• Intravenous drug users
• Concomitant HIV patients
• "HBV/HCV screening should be provided in conjunction with STD screening, at intervals informed by risk assessment" ^[1]

What slide 22's collage is showing: elimination is layered rather than a single screening campaign. The global 2022-2030 strategy supplies goals; Hong Kong's action plans translate them locally; micro-elimination focuses resources on groups such as dialysis patients, people who inject drugs and people living with HIV; linkage with sexual-health services creates additional testing opportunities. Policy, targeted service design and primary-care delivery must connect.

Key findings (Wong WC as co-first author):

1. Universal HBV screening in China is cost-effective
2. Data robust in different sensitivity analyses
3. Can save 3.46 million lives
4. Impact decreases if screening is delayed
5. Screening alone cannot reduce mortality by 65% — treatment uptake is also essential

Methodology ^[1]:

• Markov decision-analytic model simulating HBV natural history
• Examined 15 target groups stratified by age (18-30, 18-40, 18-50, 18-60, 18-70 years), born before HBV vaccine was integrated into the Chinese national immunisation programme (free since 2002)
• Four screening strategies compared:
  1. HBsAg alone
  2. HBsAg + HBsAb
  3. HBsAg + HBsAb + HBcAb
  4. HBsAg + HBsAb + HBeAg + HBeAb + HBcAb ("Five-test" panel)
• Three initiation years: 2021, 2026, 2031 (to show cost of delay)

Slide 25 presents the modelling workflow visually:

Sensitivity analysis asks whether the conclusion survives plausible changes in uncertain inputs; it is not merely a repeat of the base-case calculation.

Model result: The five-test (HBsAg/anti-HBs/HBeAg/anti-HBe/anti-HBc) strategy for people aged 18–70 was the most cost-effective of the modelled China strategies and start years. ^[1]

This is an economic-model result for a defined Chinese population and set of assumptions—not a universal instruction to order five markers for every patient in every health system.

How to read slide 27: the horizontal axis is incremental QALYs and the vertical axis is incremental cost. The diagonal line represents the model's willingness-to-pay threshold (one-times GDP per capita); strategies below that line are considered cost-effective under that threshold. The three panels repeat the comparison for starts in 2021, 2026 and 2031, making the cost of delay visible. The labelled five-marker, age 18-70 point is the preferred modelled strategy—not proof that it is the best clinical test panel everywhere.

Why five tests? Each serological marker tells you something different:

• HBsAg: Currently infected?
• HBsAb: Immune (from vaccine or resolved infection)?
• HBcAb: Ever been exposed (past or current)?
• HBeAg: Often correlates with higher replication/infectivity, but HBV DNA is the direct replication measure
• Anti-HBe: Often follows e-antigen seroconversion, but precore/basal-core-promoter variants can still replicate despite anti-HBe

Together these markers help classify current infection, past exposure and vaccine immunity, but they do not by themselves determine who needs antiviral treatment. Current care requires confirmation and clinical staging—typically including HBV DNA, ALT and assessment of fibrosis/cirrhosis, with evaluation for coinfections and comorbidity as appropriate. The 2024 WHO guideline explicitly links improved diagnosis to reflex/point-of-care HBV DNA testing and simplified treatment eligibility ^[16].

The model follows people through recurrent health states rather than a simple one-way line:

• unprotected → acute infection, chronic carrier/active CHB, resolved infection or immunised;
• carrier state can move to active CHB and back;
• active CHB can progress to compensated cirrhosis;
• cirrhosis can decompensate or develop HCC;
• HCC may lead to transplantation; decompensation, HCC and transplantation all carry HBV-related mortality.

The self-loops in the image mean a person can remain in the same state for another model cycle. Screening changes when infection is recognised; treatment changes the transition probabilities toward cirrhosis, HCC and death.

The new WHO strategies recommend decentralising routine hepatitis testing and care to primary care. ^[1]

The lecture presents a second cost-effectiveness study comparing three scenarios:

Model assumptions shown on slide 30: a cohort of 100,000 adults aged at least 18 was simulated; the model used the five-marker serology strategy, and primary-care treatment was limited to oral nucleos(t)ide analogues rather than interferon. These are analytical assumptions, not a complete clinical protocol.

How to read the decision trees (slide 31): the status quo sends diagnosed patients to specialty care at first contact. Scenario 2 moves testing and routine follow-up to primary care but keeps treatment initiation in specialty care. Scenario 3 also moves treatment initiation for suitable stable patients into primary care, while predefined high-risk, severe/suboptimally responsive or deteriorating patients cross the interface to specialty care. The visual lesson is task shifting with explicit safety-net referral, not replacement of specialists.

"Improving HBV antiviral treatment uptake is the key to improving the shared-care models' effectiveness and cost-effectiveness." ^[1]

Why this is clinically important: The decision trees compare where testing, follow-up and treatment initiation occur. Their message is that decentralisation can reduce bottlenecks if primary-care capacity, treatment uptake and referral rules are adequate. The cost and outcome figures are projections from the model, not observed results from a randomised service rollout.

The lecture outlines a multi-pronged approach:

1. Policy and Guideline — e.g., HBV guideline for primary care in Mainland China (11,552 online reads)
2. Evidence to do better — e.g., universal screening research
3. Engaging medical professionals and industries
4. Traditional and Digital Media — World Hepatitis Day promotion videos (FB views: 435,030), social media campaigns
5. Community Outreach — vulnerable HCV communities, media coverage (18 outlets)
6. Within and Beyond Hong Kong and China — BBC Future series, YouTube/social media channels

Why this matters for exams: Health promotion is not just about clinical knowledge — it's about communication, community engagement, policy advocacy, and using multiple channels to reach people. Family Medicine questions may ask about barriers to health promotion and how to overcome them.

What the image-heavy final sequence adds (slides 33-39): the same intervention is shown moving through successive implementation layers:

1. Build professional capacity: Mainland primary-care training reached a slide-reported online attendance of 4,787; a guideline-based national case competition tested lifelong CHB management.
2. Change service use: the HKU-Shenzhen Family Medicine clinic panel reports a 62% rise in HBV patient attendance in 2021—an historical local implementation indicator, not a controlled-effect estimate.
3. Create public reach: World Hepatitis Day used clinician/celebrity videos, traditional media and social platforms; the 435,030 Facebook views measure reach, not diagnosis, treatment or health outcome.
4. Reach excluded groups: the HCV outreach collage contrasts undifferentiated population activity with targeted micro-elimination in vulnerable communities and links outreach to evaluation/publication.
5. Scale beyond one locality: the BBC, YouTube and clinician-channel images show translation of the same education message across local and international audiences.

This is the lecture's core implementation chain: evidence → guideline/policy → workforce capability → accessible services → targeted/community communication → measured reach and outcomes.

The prevention principle is stable, but exact maternal prophylaxis, infant HBIG/vaccine timing, post-vaccination testing and treatment/surveillance thresholds must follow the current local protocol and specialist guideline. WHO now recommends birth-dose vaccination within 24 hours and uses HBV DNA/liver-disease assessment in the modern care pathway ^[16][17].

• "Name the levels of prevention": List all four (Primary, Secondary, Tertiary, Quaternary) with one-line definitions.
• "State the Wilson-Jungner criteria": List all 5 condensed points (or full 10 if asked). The 5-point version from this lecture is sufficient for FM questions.
• "What is quaternary prevention?": "Action to identify patients at risk of over-medicalisation and protect them from unnecessary medical interventions" — must include the concept of harm from medicine itself.