Distribution of molecular strains of Mycobacterium tuberculosis in an intermediate burden Asia Pacific city.

Hong Kong is an intermediate tuberculosis (TB) burden city in Asia Pacific with slow decline of case notification in the last decade. By 24-loci mycobacterial interspersed repetitive units - variable number of tandem repeats genotyping, we examined 534 Mycobacterium tuberculosis isolates collected from culture-positive hospitalised TB patients in a 1.7 million population geographic region in the city. Overall, 286 (75%) were classified as Beijing genotype, of which 216 (76%) and 59 (21%) belonged to modern and ancient sub-lineage, respectively. Only two cases were genetically clustered while spatial clustering was absent. Male gender, permanent residency in Hong Kong and born in Hong Kong or Mainland China were associated with Beijing genotype. The high prevalence of Beijing modern lineage was similar to that in East Asia, which reflected the pattern resulting from population migration. The paucity of clustering suggested that reactivation accounted for most of the TB disease cases, which was and echoed by observation that half were 60 years old or above, and the presence of co-morbid medical conditions. The predominance of reactivation TB cases in intermediate burden localities implies that the detection and control of latent TB infection would be the major challenge in achieving TB elimination.

Latent Tuberculosis Infection Testing Strategies for HIV-Positive Individuals in Hong Kong.

Importance: With immune recovery following early initiation of antiretroviral therapy (ART), the risk of tuberculosis (TB) reactivation among individuals with HIV could be reduced. The current strategy of annual latent TB infection (LTBI) testing should be revisited to increase cost-effectiveness and reduce the intensity of testing for individuals. Objective: To analyze the cost-effectiveness of LTBI testing strategies for individuals in Hong Kong with HIV who had negative LTBI test results at baseline. Design, Setting, and Participants: This decision analytical model study using a cost-effectiveness analysis included 3130 individuals with HIV in Hong Kong, China, which has an intermediate TB burden and a low incidence of HIV-TB coinfection. A system dynamics model of individuals with HIV attending a major HIV specialist clinic in Hong Kong was developed and parameterized by longitudinal clinical and LTBI testing records of patients during a 15-year period. The study population was stratified by age group, CD4 lymphocyte level, ART status, and right of abode. Alternative strategies for LTBI testing after a baseline test were compared with annual testing under different coverages of ART, LTBI testing, and LTBI treatment scenarios in the model. An annual discounting rate of 3.5% was used in cost-effectiveness analysis. Main Outcomes and Measures: Proportion of new TB cases averted above base case scenario, discounted quality-adjusted life-years gained (QALYG), incremental cost, and incremental cost-effectiveness ratios in 2017 to 2023. Results: A total of 3130 patients with HIV (2740 [87.5%] male and 2800 [89.5%] younger than 50 years at HIV diagnosis) with 16 630 person-years of follow-up data from 2002 to 2017 were analyzed. Of these, 94 patients (0.67 [95% CI, 0.51-0.91] per 100 person-years) developed TB. Model estimates of cumulative number of TB cases would reach 146 by 2023, with the annual number of new TB diagnoses ranging from 6 to 8. For patients who had negative LTBI test results at baseline, subsequent LTBI testing strategies were ranked by ascending effectiveness as follows: (1) no testing, (2) test by risk factors, (3) biennial testing for all, (4) up to 3 tests for all, and (5) annual testing for all. Applying a willingness-to-pay threshold of $50 000 per QALYG, none of the subsequent testing strategies were cost-effective. Test by risk factors and up to 3 tests for all were cost-effective only if the willingness-to-pay threshold was increased to $100 000 per QALYG and $200 000 per QALYG, respectively. More new TB cases would be averted by expanding LTBI testing and/or treatment coverage. Conclusions and Relevance: Changing the current testing strategy to less intense testing strategies is likely to be cost-effective in the presence of an increased coverage of baseline LTBI testing and/or treatment.