One Step toward a Low Tuberculosis-Burden Country: Screening for Tuberculosis Infection among the Immigrants and Refugees

Incidence of Tuberculosis Among Immigrants in Korea Who Participated in a Latent Tuberculosis Infection Screening Program

BACKGROUND

With a rapid decrease in tuberculosis (TB) incidence, the significance of latent tuberculosis infection (LTBI) has been underscored in South Korea. Although South Korea does not have a high proportion of immigrants compared to other countries, there is a growing argument that it should actively embrace immigrants as a solution to address issues of low birth rates and population aging. This study aimed to assess TB incidence among immigrants who participated a pilot LTBI screening program in South Korea.

METHODS

Records of immigrants participated in a pilot LTBI screening program in South Korea between 2018 and 2019 were linked with Korean National TB Surveillance System to determine TB development. Participants underwent interferon-gamma release assay (IGRA) and chest X-rays. Standardized incidence ratios (SIRs) stratified by age, country of origin's TB burden was calculated with a reference group of general South Korean population.

RESULTS

Of a total of 9,517 participants, 14 TB cases were identified. Participants with positive IGRA results who did not initiate LTBI treatment showed TB incidence of 312.5 per 100,000 person-years, whereas those with negative results showed TB incidence of 34.4 per 100,000 person-years, resulting in an incidence rate ratio of 9.08 (95% confidence interval [CI], 2.50-32.99). SIR of TB among total participants including those with negative IGRA results was 2.60 (95% CI, 1.54-4.38; P < 0.001), whereas SIR among those with positive IGRA results was 5.86 (95% CI, 3.15-10.89; P < 0.001). In the calculation of SIR among participants with positive IGRA results, those aged under 35 from high TB-burden countries or intermediate TB-burden countries showed a high SIR (18.08; 95% CI, 2.55-128.37; P = 0.004), and 11.30 (95% CI, 2.82-45.16; P < 0.001), respectively). Contrary to previous reports that suggest the majority of elderly population with a positive IGRA result were due to remote infection and had a lower TB risk compared to younger ages, SIR among those aged 65 or over from intermediate TB-burden countries was 6.15 (95% CI, 0.87-43.69; P = 0.069), which was comparable to that in younger participants aged between 35 and 49 (SIR, 4.87; 95% CI, 1.22-19.49; P = 0.025) or those aged between 50 and 64 (SIR, 4.62; 95% CI, 1.73-12.31; P = 0.002).

CONCLUSION

Young immigrants with positive IGRA results from countries with high or intermediate TB burden showed a relatively high TB risk compared to a general South Korea population. In addition, unexpected high TB risk was observed among elderly immigrants with positive IGRA results. In establishing future policies for LTBI in immigrants in South Korea, screenings should primarily focus on younger age group (who aged under 35). Additionally, further research is needed on the high TB risk observed in elderly immigrants.

Impact of National Public-Private Mix and Medical Expense Support Program to Control Tuberculosis in South Korea: An Interrupted Time Series Analysis

Tuberculosis (TB) remains a major threat to global public health. Various measures at the national level have been implemented to control TB, and no evidence with long-term effectiveness has yet been evaluated on TB control programs. We confirmed the long-term effectiveness of the TB control programs in reducing overall burden in South Korea using interrupted time series analysis. Our finding suggests that, along with the public-private mix, relieving the economic burden of people with TB may complement achieving the End TB Strategy. For countries currently developing strategies for TB control, results may provide important insights in effective TB control.

A Quasi-experimental Study on the Effect of Pre-entry Tuberculosis Screening for Immigrants on Treatment Outcomes in South Korea: A Difference-in-Differences Analysis

OBJECTIVE

This study ascertains the effects of the pre-entry tuberculosis (TB) screening policy, which was implemented as a strategy for managing TB among immigrants, on the treatment outcomes of immigrants in South Korea.

METHODS

This study linked three different datasets from 2013 to 2018, namely (1) Korean National Tuberculosis Surveillance System; (2) National Health Information Database for patients diagnosed with TB with ICD code A15-A19, B90, or U84.3; and (3) Statistics Korea database related to cause of deaths. To identify the effect of the policy, cohorts comprising Korean and immigrant TB patients notified before (January 1, 2013-December 31, 2015) and after (September 1, 2016-December 31, 2018), the implementations of the policy were established. A difference-in-differences (DID) analysis of the treatment success and mortality rates was performed.

RESULTS

Data from 100,262 TB patients were included in the analysis (before policy implementation: 1240 immigrants and 65,723 Koreans; after policy implementation: 256 immigrants and 33,043 Koreans). The propensity score matching-DID analysis results showed that the difference in the treatment success rate between immigrants and Koreans decreased significantly, from 16% before to 6% after the policy implementation. The difference in the mortality rate between the two groups decreased from - 3% before to - 1% after the policy implementation; however, this difference was insignificant.

CONCLUSION

The treatment outcomes of immigrant TB patients in South Korea improved after the implementation of the pre-entry active TB screening policy. Future immigrant TB policies should consider establishing active patient support strategies and a healthcare collaboration system between countries.

Latent Tuberculosis Cascade of Care Among Healthcare Workers: A Nationwide Cohort Analysis in Korea Between 2017 and 2018

BACKGROUND

In 2017, Korea implemented nationwide latent tuberculosis infection (LTBI) project targeting healthcare workers (HCWs). We aimed to assess its performance using the cascade of care model.

METHODS

We included 45,503 employees of medical institutions with positive interferon-gamma release assay result who participated between March 2017 and December 2018. We described percentages of LTBI participants completing each step in the cascade of care. Poisson regression model was conducted to assess individual characteristics and factors associated with not-visiting clinics for further care, not-initiating LTBI treatment, and not-completing treatment.

RESULTS

Proportions of visiting clinics and initiating and completing treatment in HCWs were 54.9%, 38.5%, and 32.0%, respectively. Despite of less likelihood of visiting clinics and initiating LTBI treatment, older age ≥ 65 years were more likely to complete treatment (adjusted relative risk [aRR], 0.80; 95% confidence interval [CI], 0.64-0.99), compared to young age < 35 years. Compared to nurses, doctors were less likely to visit clinic; however, were more likely to initiate treatment (aRR, 0.88; 95% CI, 0.81-0.96). Those who visited public health centers were associated with not-initiating treatment (aRR, 1.34; 95% CI, 1.29-1.40). When treated at private hospitals, 9-month isoniazid monotherapy was less likely to complete treatment, compared to 3-month isoniazid and rifampicin combination therapy (aRR, 1.33; 95% CI, 1.16-1.53).

CONCLUSION

Among employees of medical institutions with LTBI, only one third completed treatment. Age, occupation, treatment center, and initial regimen were significantly related to LTBI treatment performance indicators. Rifampicin-based short treatment regimens were effective under standard of care.

Comparison of Disability-Adjusted Life Years (DALYs) and Economic Burden on People With Drug-Susceptible Tuberculosis and Multidrug-Resistant Tuberculosis in Korea

In the future, tuberculosis (TB) will place a heavy burden on the aging population in Korea. To prepare for this crisis, it is important to analyze the disease burden trend of drug-susceptible tuberculosis (DS-TB) and multidrug-resistant tuberculosis (MDR-TB). Measuring disability-adjusted life years (DALYs) and economic burden on MDR-TB patients can help reduce the incidence of TB. Accordingly, in this study, we measured the DALYs and economic burden on DS-TB and MDR-TB patients in 2014-2017 using a combination of National Health Insurance claims data, Annual Report on the Notified TB data, and Statistics Korea's mortality data. The incidence-based DALY approach implemented involved the summation of years of life lost and years lived with disability. For measuring economic burden, direct and indirect costs incurred by patients were totaled. From 2014 to 2017, DALYs per 100,000 people with DS-TB were 56, 49, 46, and 40, respectively, and DALYs per 100,000 people with MDR-TB were 3, 2, 2, and 2, respectively. The economic burden for the DS-TB population from 2014 to 2017 was $143.89 million, $136.36 million, $122.85 million, and $116.62 million, respectively, while that for MDR-TB was $413.44 million, $380.25 million, $376.46 million and $408.14 million, respectively. The results showed a decreasing trend in DALYs and economic burden for DS-TB, whereas MDR-TB was still found to be burdensome without a specific trend. With respect to age, the economic burden for both DS-TB and MDR-TB was higher among men than among women till ≤ 79 years. Conversely, the economic burden for women aged ≥80 years was higher as compared to their male counterparts. In conclusion, the incidence and spread of TB in all areas of society must be suppressed through intensive management of MDR-TB in the older population. We hope that the national TB management project will proceed efficiently when the infectious disease management system is biased to one side due to the COVID-19 pandemic.

The burden and predictors of latent tuberculosis infection among immigrants in South Korea: a retrospective cross-sectional study

BACKGROUND

Approximately one-fourth of the global population is latently infected with Mycobacterium tuberculosis. An understanding of the burden of latent tuberculosis infection (LTBI) among immigrants compared with the general Korean population should be the first step in identifying priority groups for LTBI diagnosis and treatment. The study aimed to compute the age-standardized LTBI prevalence and predictors among immigrants with LTBI in South Korea.

METHODS

In 2018, the Korea Disease Control and Prevention Agency implemented a pilot LTBI screening project for immigrants using a chest radiography and the QuantiFERON Gold In-Tube assay. A standardized prevalence ratio (SPR) was computed to compare the LTBI burden in immigrants and the general Korean population.

RESULTS

During the duration of the project, a total of 8108 immigrants (5134 males and 2974 females) underwent LTBI screening. The SPR of 1.547 (95% confidence interval [CI] 1.468-1.629) in males and 1.261 (95% CI 1.177-1.349) in females were both higher than the Korean reference population. Furthermore, among the immigrants, those aged < 40 years and Korean diaspora visa holders had a higher SPR.

CONCLUSION

This study found a higher LTBI prevalence among immigrant population in South Korea compared to that in the general Korean population, and the SPR was higher among those aged < 40 years and the Korean diaspora. The findings can be used as baseline evidence for including immigrants in South Korea in the at-risk group with a priority need for LTBI screening and treatment.

Evaluating the impact of the nationwide public-private mix (PPM) program for tuberculosis under National Health Insurance in South Korea: A difference in differences analysis

BACKGROUND

Public-private mix (PPM) programs on tuberculosis (TB) have a critical role in engaging and integrating the private sector into the national TB control efforts in order to meet the End TB Strategy targets. South Korea's PPM program can provide important insights on the long-term impact and policy gaps in the development and expansion of PPM as a nationwide program.

METHODS AND FINDINGS

Healthcare is privatized in South Korea, and a majority (80.3% in 2009) of TB patients sought care in the private sector. Since 2009, South Korea has rapidly expanded its PPM program coverage under the National Health Insurance (NHI) scheme as a formal national program with dedicated PPM nurses managing TB patients in both the private and public sectors. Using the difference in differences (DID) analytic framework, we compared relative changes in TB treatment outcomes-treatment success (TS) and loss to follow-up (LTFU)-in the private and public sector between the 2009 and 2014 TB patient cohorts. Propensity score matching (PSM) using the kernel method was done to adjust for imbalances in the covariates between the 2 population cohorts. The 2009 cohort included 6,195 (63.0% male, 37.0% female; mean age: 42.1) and 27,396 (56.1% male, 43.9% female; mean age: 45.7) TB patients in the public and private sectors, respectively. The 2014 cohort included 2,803 (63.2% male, 36.8% female; mean age: 50.1) and 29,988 (56.5% male, 43.5% female; mean age: 54.7) patients. In both the private and public sectors, the proportion of patients with transfer history decreased (public: 23.8% to 21.7% and private: 20.8% to 17.6%), and bacteriological confirmed disease increased (public: 48.9% to 62.3% and private: 48.8% to 58.1%) in 2014 compared to 2009. After expanding nationwide PPM, absolute TS rates improved by 9.10% (87.5% to 93.4%) and by 13.6% (from 70.3% to 83.9%) in the public and private sectors. Relative to the public, the private saw 4.1% (95% confidence interval [CI] 2.9% to 5.3%, p-value < 0.001) and -8.7% (95% CI -9.7% to -7.7%, p-value <0.001) higher rates of improvement in TS and reduction in LTFU. Treatment outcomes did not improve in patients who experienced at least 1 transfer during their TB treatment. Study limitations include non-longitudinal nature of our original dataset, inability to assess the regional disparities, and verify PPM program's impact on TB mortality.

CONCLUSIONS

We found that the nationwide scale-up of the PPM program was associated with improvements in TB treatment outcomes in the private sector in South Korea. Centralized financial governance and regulatory mechanisms were integral in facilitating the integration of highly diverse South Korean private sector into the national TB control program and scaling up of the PPM intervention nationwide. However, TB care gaps continued to exist for patients who transferred at least once during their treatment. These programmatic gaps may be improved through reducing administrative hurdles and making programmatic amendments that can help facilitate management TB patients between institutions and healthcare sectors, as well as across administrative regions.

Current situation of tuberculosis and National Strategic Plan for Tuberculosis Control in Korea

Tuberculosis (TB) remains a serious public health problem in Korea. Korea has the highest incidence rate (59 per 100,000 population) and the second-highest TB mortality rate (four per 100,000 population) among Organisation for Economic Cooperation and Development member countries. However, some progress has been made in TB control over the past decade. The notification rate of new TB cases has been gradually decreasing since reaching its highest rate in 2011 (78.9 per 100,000 population). In 2019, the notification rate of new TB cases was 46.4 per 100,000 population, with a reduction of 9.9% from the 2018 rate. Additionally, the number of multidrug-resistant TB cases decreased from 618 in 2018 to 580 in 2019. This progress is thought the result of various TB control programs including a TB public–private mix model, insurance coverage for TB management, and a contact investigation program. Despite the progress made, new challenges have also emerged. The predominant challenges lie in the relatively increasing burden of TB in the vulnerable population (aging, socio-economically vulnerable, and foreign-born population), the implementation of latent TB infection management, and the high rate of multidrug-resistant TB. Since 2019, the Korean government has been implementing the “Midterm strategies to strengthen TB prevention and management” based on the 2nd National Strategic Plan for Tuberculosis Control (2018-2022). This program will be a turning point of TB control in Korea. The results produced in 2023 is expected to be favorable.

Latent tuberculosis infection: recent progress and challenges in South Korea

Management of latent tuberculosis infection (LTBI) is a critical element in the elimination of tuberculosis (TB). However, the low positive predictive value of the current diagnostic tests and the low acceptance and completion rate of the isoniazid- based regimen are major barriers to the implementation and scale-up of programmatic management of LTBI. In the past decade, there has been some progress in the conception, diagnosis, and treatment of LTBI. LTBI is now understood as a dynamic spectrum rather than the traditional binary distinction between active and latent TB. New insight into LTBI has led to a renewed interest in incipient TB, which would be a potential target for developing new diagnostics and therapeutics of LTBI. Recent studies showed that host transcriptomic signatures could be a potential biomarker for incipient TB. The new shorter rifamycin-based regimens have shown comparable efficacy, but better completion rate and safety compared to the isoniazid-based regimen. In South Korea, LTBI management has been expanded and integrated into key elements of the National Tuberculosis Control Program. For the programmatic approach to LTBI management, the following challenges need to be addressed; target group selection, treatment-related interventions, monitoring and surveillance system, and extending the plan for vulnerable groups.