Flashcards in L70 – Tuberculosis: a re-emerging public menace Deck (66):
What is the estimated human population infected with MTB?
Estimated 2-3 billion people (~1/3 human population) has been infected with
How does TB rank as a cause of death?
5th leading cause
What is the disease ratio of TB (ratio of new infection to
development of overt disease) ?
Recall Tb has primary (dormant, host immune not activated) and post-primary infections:
5% > primary infection within 5 years
Further 5% > post-primary disease
What is the main diagnosis for TB?
other include rapid molecular tests, sputum smear, culture, sensitivity testing ...etc
What are the methods to estimate TB incidence?
National notification/ prevalence survey
What does the huge difference between estimated incidence and number of TB notifications mean?
That many TB patients have not been diagnosed/ treated in healthcare systems
How does estimate TB mortality rate differ in HIV patients?
HIV = more susceptible to TB
What is the trend of TB mortality in HIV-ve and +ve patients?
HIV -ve declines at a much higher rate than HIV +ve
What is the decline in TB mortality rate between 2000 and 2015?
What is the target for TB incidence rate decline by 2020
Which global regions have the fastest and slowest decline in TB mortality?
Fastest = Eastern mediterranean and Europe
Slowest = Africa
What is the difference between the countries at the top of Incidence: absolute numbers chart and Incidence: Rate chart?
Incidence: absolute numbers chart >> occupied by developing/ developed countries with huge populations (e.g. China, India) but situation is IMPROVING
Incidence: Rate chart>> occupied by undeveloped countries where situation is NOT IMPROVING
The top 6 countries with the largest number of incident cases account for __ % of global total ?
What are some predisposing factors to TB?
Age (adult predominant)
Sex (male predominant)
Prior mycobacterial infection
Confounded by socio-economic and environmental conditions
What are the stats on TB propagation in a community? (how many people can infection pass onto...)
Each infection on average produces ≥ 1 secondary infection
Each untreated infects 20-28 persons
6-10% develop active disease
How many cases of infectious TB is considered an endemic?
How does the supply of susceptible individuals compare to the rate of being infected by TB?
Supply of susceptible ≥ Rate of being infected
Supply can be from birth, immigration..etc to increase population size
What is the reproductive ratio (r0)?
Estimation of the rate of infection spread
Given TB declined before medication or vaccines, what causes the most impact in reducing TB incidence?
Improve hygiene and public health
What are the 5 risk factors of POVERTY that affects rate of community acquired TB?
E H PSP
Ed Has a PSP
How does poverty lead to increased risk of getting TB?
Poverty itself cannot cause TB,
but poor living conditions in many complex interacting pathways could affect the risk of getting TB
What are the 3 components of living condition?
-Community (e.g. housing density, planning, access, pollution...)
-Household (e.g. crowded, ventilation, security...)
-Individual (e.g. economic status, smkoing, cancer, abus...)
How many TB cases are due to smoking?
20% attributable to TB
How many times greater is the risk of TB given HIV=ve?
20-30x greater than HIV
Why doe TB have atypical presentation in HIV patients?
Poorer outcomes (HIV progresses very fast)
Less infectious (smear negative) but still transmissible
What does HRZES refer to in TB drugs?
Presi > Zresh
isoniazid (H), rifampicin (R), pyrazinamide (Z), ethambutol (E), streptomycin (S)
What are the combos for First line TB drugs?
2HRZE(S) [2 months]; or
4HR [4 months]
* isoniazid (H), rifampicin (R), pyrazinamide (Z), ethambutol (E), streptomycin (S)
What is XDR-TB resistant to?
At least H, R + an injectiable drug + a fluoroquinolone
2nd line TB drugs?
Which cases of TB should be treated with second line MDR-TB treatment?
Rifampcin resistant TB and MDR-TB
What are the main causes of drug-resistance TB?
Unregulated OTC drug sale
Poor supervision of therapy
What are some supply/ production issues of TB drugs that lead to resistance
Intermittent drug supplies
Combo preparation is poorly done or unavailable
Usage of expired drugs
What is the DOTS stratgey and when is it used?
Directly observed therapy, short course
>> core component of End TB Strategy for controlling TB
What is the purpose of DOTS? (think funding and drugs)
Ensure uninterrupted access to high quality anti-TB drugs and adequate money for complete course of antibiotics
What are the new MDR/RR-TB drugs ?
Why is treatment of MDR/RR-TB not that successful?
Shortage of trained staff
Limited market > all options very expensive
Not enough number of facilities for treatment and monitoring
What is the Vision and Goal of the End TB strategy?
Vision: zero deaths and suffering due to TB
Goal: End the Global TB epidemic
3 pillars of End TB Startegy?
1. Integrated, patient-centred
care and prevention
2. Bold policies and supportive systems
3. Intensified research and innovation
2 criteria for the TB high-burden country list?
Top 20 in terms of absolute number of TB cases
Meet threshold of incidence rate per capita
Compare rate of incidence of TB in hong kong vs western countries?
Western = less than 10/100,000
HK = 58/100,000
Give 3 reasons for the drop in TB notification rate in HK over the last 40 years?
1) Ageing population **
2) Improved surveillance and reporting
3) Long latency of reactivation > increasing proportion of TB cases
Why did rate of TB drop during WWII when the conditions should increase incidence?
Breakdown of infrasturcture for surveillance and reporting = under-report rates
Compare the age groups affected by Progressive primary infection and non-primary infections of TB?
Primary = younger
Non-primary = reactivation = older
What age group most affected by MDR and MDR-TB?
age group = middle aged
Is TB notification compulsory in HK?
Yes, Notified by law, send to Department of Health
What is the use of notification of TB?
Initiation of contract tracing
Provide info about epidemiology of TB
What are centers for TB services?
Directly approach DoH CHEST CLINIC
Referral from private practice, GOPD
Number of TB Chest clinics? Managed by?
17 HK TB and Chest Service centers
Managed by DoH
What are the 3 ways DoH chest clinics improve service to help treat TB?
- Free treatment
- Ant-TB meds and treatment are given under FULL supervision (avoid incomplete course of meds...etc)
- Extended opening time > accessibility
What is the lab supporting DoH chest clinics?
TB Reference Lab of DoH
Give the reasons for HA to admit a TB patient for inpatient, given most TB cases are outpatient?
- Social reasons/ problems with adherence (e.g. retarded)
- disease complication
- treatment complication
- other medical conditions
- Investigations (e.g. bronchoscopy)
What are the most important stretgies for controlling TB in HK?
- Case finding
- Effective chemotherapy
- Treat latent TB infection
- BCG vaccine
(+ health education)
What are the low and high cost effectiveness screening strategies for TB?
Low: Mass CXR (no longer done in HA)
High: Screening contacts/ contact-tracing
What is the approach of contact tracing?
' concentric circle apporach' > people in very close contact examined first
Difference in the screen tests done for active TB and latent TB infection?
Active = CXR, clinical symptoms, sputum microscopy
Latent: Tuberculin skin test (Purified Protein Derivative...etc )
Is CXR effective for screening TB in HIV patients?
No, low yield
What processes follow smear +ve and smear +ve results from TB contact investigations?
Smear +ve = start clinical treatment immediately
Smear -ve = CXR (sometimes +Tuberculin skin test)
What is passive case finding?
Walk-in, self-reported cases with symptomatic patients
Cost effective, accounts for over 90% TB cases in HK
What is important to achieving effective chemotherapy?
Effective regimes are prescribed
High Patient adherence to treatment and duration
Why is ineffective chemotherapy TB worse than no therapy?
Increase resistance of TB
Increased risk of repeated relapses
>> chronic infections
2 benefits to improve diagnosis and treatment of latent TB infection?
Reduce pool of infected in populaiton
Rapid control over disease
What are some problems of treatment of Latent TB infections?
Imperfect diagnostic tools (e.g. hard to interpret positive tuberculin skin test given high BCG coverage)
Difficult to achieve patient adherence (hard to motivate, commit)
Prologned course have side effects
What are the high risk groups in latent TB infections?
Infants with close contact with smear +ve patients
Similar aged contacts under 35 (with at least 15m tuberculin response/ conversion from -ve to +ve result)
Tuberculin +ve, HIV-infected or silicosis
Which age group is protected by BCG?
BCG is given to all newborn and children under 15 without vaccination
Why is health education important to combat TB?
Promote passive case finding
Improve patient adherence to treatment
>> not to set rules, but to reach mutual understanding/ partnership