Abstract
Hong Kong is a high-income city with intermediate tuberculosis (TB) burden primarily driven by endogenous reactivations. A high proportion of remote latently infected people, particularly elderly, hinders the effectiveness of current strategies focusing on passive TB detection. In this study, we developed a mathematical model to evaluate the impact of treating latent TB infection (LTBI) in the elderly in addition to current TB control strategies. The model was calibrated using the annual age-stratified TB notifications from 1965–2013 in Hong Kong. Our results showed that at present, approximately 75% of annual new notifications were from reactivations. Given the present treatment completion rate, even if only a low to moderate proportion (approximately 20% to 40%) of elderly people were screened and treated for LTBI, the overall TB incidence could be reduced by almost 50%, to reach the 2025 milestone of the global End TB Strategy. Nevertheless, due to a high risk of hepatotoxicity in elderly population, benefit-risk ratios were mostly below unity; thus, intervention programs should be carefully formulated, including prioritising LTBI treatment for high-risk elderly groups who are closely monitored for possible adverse side effects.
Highlights
Hong Kong is a high-income city with intermediate tuberculosis (TB) burden primarily driven by endogenous reactivations
In the retrospective validation using 2004–2013 data, we showed that the R-square, mean absolute error (MAE), and mean absolute percentage error (MAPE) of the model simulation were 89.5%, 6.8/100,000, and 8.2% respectively which indicated a high consistency in model prediction
The high number of latent TB infection (LTBI) cases in elderly individuals and the associated risk of reactivation poses a challenge to TB control, with management in this population likely to improve control
Summary
Hong Kong is a high-income city with intermediate tuberculosis (TB) burden primarily driven by endogenous reactivations. Given the present treatment completion rate, even if only a low to moderate proportion (approximately 20% to 40%) of elderly people were screened and treated for LTBI, the overall TB incidence could be reduced by almost 50%, to reach the 2025 milestone of the global End TB Strategy. Cases resulting from primary infection and reinfection have decreased in Hong Kong, current measures using passive screening and Directed Observed Treatment, Short-course (DOTS) are insufficient as it only helps reducing recent transmissions but is unable to prevent active TB development from reactivation from remote infection, which has become the main source of TB incidence as with many intermediate burden areas[1,2,3]. To inform future LTBI management strategies, we investigated the public health impact of an expanded LTBI screening and treatment program targeting the elderly, as the high number of reactivated cases is a barrier for TB prevention
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