L70: Tuberculosis a Re-emerging Public Menace

Question 1

Global situation of TB

Answer 1

• 5th cause of death worldwide
• 2-3 billion (1/3 global population) people infected
• 70% smear-positive died within 10 years without TB treatment
• rapid molecular tests for diagnosis available
• considerable proportion still clinically diagnosed

Question 2

Methods used to estimate TB incidence

Answer 2

1. Vital registration system
2. Notification and surveillance system
3. Prevalence survey

Question 3

TB incidence rates and mortality rate

Answer 3

• Global decline in TB incidence rate by 1.5%
• Mortality rate fell by 34%
• Top 6 with largest number of incidence case account for 60% global total
• Incidence rate: fastest decline in EU
• Mortality rate: fastest decline in Eastern Mediterranean + EU
• Mortality rate: slowest decline in African region

Question 4

Predisposing factors for Tb

Answer 4

• Age
• Male
• HIV (major risk factor, 1/3 deaths due to TB, atypical + late presentation, increased transmission, much higher case-fatality rate, stigma affecting health-seeking behaviour)
• DM
• Poverty
• Tobacco smoke
• Malnutrition
• Prior mycobacterial infection
• Chemotherapy
• Genetics

Social RF

• Economic
• Human
• Political
• Socio-cultural
• Protective (vulnerability)

Confounded by socioeconomic and environmental conditions

• Community (high population density, inefficient healthcare, housing planning)
• Household (poor food security, poor income, poor ventilation)
• Individual (socio-economic status, smoking, HIV, DM)

Question 5

Propagation in community

Answer 5

• each invention produce more than 1 secondary infection
• supply of susceptible individuals > rate of being infected
• high risk settings: undiagnosed + close contact + risk factors

Question 6

Drug resistant TB

Answer 6

RR-TB - resistant to at least Rifampicin
MDR-TB - resistant to at least Isoniazid + Rifampicin
XDR-TB - resistant to at least Isoniazid + Rifampicin + injectable + Fluoroquinolone

2nd line:

• injectable (amikacin, kanamycin, capreomycin)
• fluoroquinolone

All cases of RR-TB and MDR-TB should be treated with 2nd line treatment

Question 7

Reasons for drug-resistant TB

Answer 7

• Poor supervision of therapy —> DOTS
• intermittent drug supplies
• unavailability of combination
• poorly-formulated combination
• addition of single drug to failing regimen in absence of bacteriologic control

Question 8

DOTS strategy

Answer 8

Directly observed therapy, short-course

• Core component of End TB strategy
• uninterrupted access to high quality anti-TB drug
• 6 month course, $40
• success rate >=85% for drug-susceptible TB

Question 9

Treatment of MDR/RR-TB

Answer 9

2nd line treatment: 9-12 months, $1000, >= 70% success

Novel drug: Bedaquiline, Delamanid

Question 10

*End TB strategy

Answer 10

Vision: World free of TB —> 0 deaths, disease and suffering due to TB

Goal: end global TB epidemic, End-TB: 2035

Principles

1. Government stewardship and accountability, monitoring, evaluation
2. Coalition with Civil society organisations and communities
3. Protection and promotion of human rights, ethics and equity
4. Adaptation of strategy at country level, with global collaboration

Pillars and components

1. Patient-centred care and prevention, early diagnosis
2. Bold policies and supportive system
3. Intensified research and innovation

Question 11

TB in Hong Kong

Answer 11

• higher than other modern communities such as Japan and Singapore
• relatively high incidence
• ageing population: reactivation of old infection / new infection
• Case notification rate per 100,000: 66.4%
• death rate due to TB: 2.2%

TB notification rate
- falling notification rate
—> ageing population
—> improved surveillance and reporting (must be notified by law: 1. Contact tracing and 2. Provide information about epidemiology)
—> long latency of reactivation
- Greater decline in primary infection (younger population)
- Slower decline in endogenous reactivation (older population)

Question 12

TB services and referral patterns

Answer 12

Hong Kong Tuberculosis and Chest Service (by DoH)

• free of charge
• TB treatment given under full supervision
• supported by TB Reference Laboratory of DH (receives specimens from HA hospital, private labs and doctors)

Hospital Authority

• investigation
• management of complications
• complications of treatment
• other medical condition
• social reasons / problems with adherence (psychiatric illness)

Question 13

***Strategy for control of TB in HK

Answer 13

1. Case finding
   - screening contacts of TB cases (1%): concentric approach
   - symptomatology, CXR, sputum microscopy (active TB), tuberculin skin test (latent TB)
   - passive case finding: mainstay in Hong Kong
   —> symptomatic patient come forward (smear positive)
   —> cost effective, walk-in, free service, no need referral
2. Effective chemotherapy
   - effective regimens prescribed
   - patient adherence —> supervised therapy
3. Treatment of latent TB infection
   - Problems: imperfect diagnostic tool, serious SE from prolonged course of treatment, high BCG coverage (false-positve), difficult to motivate perfectly well individual to treatment
   - infant close contacts
   - under 35 (tuberculin response >=15mm / tuberculin conversion)
   - HIV individuals
   - silicosis
4. BCG vaccination (newborns and under 15 not had before)
   - attenuated M. bovis
   - preventing severe forms of TB in children
   - NOT in preventing TB in adults
5. Health education
   - raise awareness, reduce stigma
   - promote passive case-finding
   - adhere to treatment (patient may mistake improvement during treatment as cure)
   - barrier to adherence:
   —> work problems
   —> family support
   —> financial status
   —> housing conditions
   —> health beliefs