Page 19 - HA Convention 2016 [Abstracts (Day 1)]

Special Topics HOSPITAL AUTHORITY CONVENTION 2016

T5.3 Latest Development of Tuberculosis Management 14:30 Theatre 2

Targeted Screening and Treatment of Latent Tuberculosis Infection in Hong Kong Tuesday, 3 May
Chang KC
Tuberculosis and Chest Service, Department of Health, The Government of the Hong Kong Special Administrative Region

Latent infection with Mycobacterium tuberculosis (LTBI) is pragmatically defined as presumptive infection with Mycobacterium
tuberculosis complex, as evidenced by a positive tuberculin skin test (TST) reaction and/or a positive interferon-ϒ release
assay (IGRA) result without any sign of clinically or radiologically manifest disease.

Existing immunodiagnostic tools for LTBI are limited in their ability to predict disease. Treatment of LTBI can decrease the
risk of TB disease by up to 90%, but is not without adverse events. To maximise cost effectiveness, screening of LTBI is best
done by a targeted approach among high-risk subjects with an intention to treat.

One-third of the world population has probably been infected by Mycobacterium tuberculosis. In Hong Kong, nearly 40% of
TB cases occur among elderly aged 65 and above, largely as a result of reactivation of LTBI. To further reduce TB morbidity
and mortality in Hong Kong, targeted screening and treatment of LTBI among high-risk persons may complement treatment
of TB disease.

Targeted screening and treatment of LTBI is locally focused on four clinical scenarios: household contacts of sputum smear-
positive patients (especially those aged <35), silicosis, HIV-infected, and immunosuppression (especially TNF blockers). The
use of different TST cutoffs for different scenarios represents a need to balance sensitivity against specificity. IGRA may be
used as an alternative or to confirm a borderline TST result, when there are concerns over BCG vaccination-induced cross-
reactivity.

When LTBI likely results from drug-susceptible tubercle bacilli, the efficacy of six to nine months of isoniazid preventive
treatment is offset by poor adherence and concerns about hepatotoxicity. Shorter alternatives include isoniazid and
rifampicin for three months, rifampicin for four months, and weekly rifapentine with isoniazid for 12 weeks.

When the source of infection is multidrug-resistant, close clinical observation for two years is usually recommended locally.

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