Tuberculosis: Republic of Korea, 2021

Nutrition Status and Comorbidities Are Important Factors Associated With Mortality During Anti-Tuberculosis Treatment

BACKGROUND

The increasing incidence and mortality rates of tuberculosis among older individuals who suffer from multiple morbidities and are vulnerable to malnutrition are major obstacles to efforts to eradicate tuberculosis in the Republic of Korea. Herein, we identified the factors associated with mortality during anti-tuberculosis treatment in patients with pulmonary tuberculosis.

METHODS

We conducted a case-control study and extracted data from the database of a multi-center prospective observational cohort study in Korea. Among the participants with rifampicin-susceptible pulmonary tuberculosis, the survival group was defined as those who successfully completed treatment within one year, whereas the mortality group was defined as those who died during treatment. Univariable and multivariable logistic regression analyses were performed to identify factors associated with TB mortality.

RESULTS

Among 1,119 participants with pulmonary TB registered between 2019 and 2021, 799 and 59 were grouped in the survival and mortality groups, respectively. Age, positive smear results, alarming symptoms, nutrition risk score, Charlson comorbidity index score, and initial standard treatment regimen were significant based on univariable analysis and were selected for the multivariable logistic regression model. Nutrition risk score (adjusted odds ratio, 2.44; 95% confidence interval, 1.72-3.48) and Charlson comorbidity index score (adjusted odds ratio, 1.62; 95% confidence interval, 1.35-1.94) remained statistically significant in the multivariate analysis.

CONCLUSION

Nutritional status and comorbidities at baseline were identified as important factors associated with mortality in patients with pulmonary tuberculosis.

Disagreement on estimating cause of death under tuberculosis treatment between the national tuberculosis registry and statistics data in South Korea, 2011-2020

BACKGROUND

Disagreement persists regarding the cause of death in patients with tuberculosis (TB) between the national TB registry and vital registration statistics. This study investigated the disagreement and contributing factors between TB-related and non-TB-related deaths using an integrated national TB database in South Korea.

METHODS

We identified a sub-set cohort of 29,033 patients with drug-susceptible TB registered between 2011 and 2020 who died during TB treatment. The cause of death was identified by the Korean National Tuberculosis Surveillance System (KNTSS) and Statistics Korea database. We performed a multinomial logistic regression to identify factors associated with the cause of death.

RESULTS

The participants' median age was 79 years (interquartile range, 70-85 years), with males comprising 63.2 %. Among the 29,033 deaths, 12,937 (44.6 %) and 6028 (20.8 %) were classified as TB-related deaths in Statistics Korea and KNTSS, respectively. The overall agreement rate for the cause of death between the two databases was 0.72 (95 % confidence interval, 0.71-0.72), increasing from 0.69 in 2011-0.77 in 2020. Among discrepant cases, 92.2 % (7545/8181) were classified as non-TB-related in KNTSS but as TB-related in Statistics Korea. Over the study period, the proportion of individuals classified as non-TB-related deaths in both databases and the agreement rate increased. In the multinomial analysis, age, sputum acid-fast bacilli smear, Charlson comorbidity index, and comorbidities, such as cancer and end-stage renal disease, showed distinguishing features across the cause of death groups.

CONCLUSIONS

Substantial disagreement on the cause of death persists between the national TB registry and vital registration statistics, though this decreased during the study period. Most disagreement likely indicates an underestimation of TB-related deaths in the TB registry. Age, sputum smear, and comorbidities were identifiable characteristics across groups that may influence the cause of death coding process.

Tuberculous and Malignant Pleural Effusions With Adenosine Deaminase Levels of 40-70 IU/L: Trends in New Cases Over Time and Differentiation Between Groups

BACKGROUND

The diagnosis of tuberculous pleural effusion (TPE) often relies on pleural fluid adenosine deaminase (ADA) levels. The diagnostic utility of ADA, however, is influenced by the prevalence of tuberculosis (TB) in local populations. Malignant pleural effusion (MPE) cases can exhibit moderately elevated ADA levels comparable to those seen in TPE. As population aging potentially impacts ADA levels, global TB incidence is decreasing whereas the burden of malignancy is on the rise. Consequently, epidemiological shifts and temporal changes in ADA distribution complicate the differential diagnosis between TPE and MPE when ADA levels are within the 40-70 IU/L range. Nonetheless, data specific to this subset are scarce.

METHODS

This retrospective study included consecutive patients aged > 18 years with confirmed TPE and MPE, spanning from 2012 to 2023. ADA levels in pleural fluid were categorized into three groups: < 40 IU/L, 40-70 IU/L, and > 70 IU/L. The study examined annual trends in the frequency of new cases and ADA level distributions over time and identified discriminating factors between TPE and MPE in cases with ADA levels of 40-70 IU/L.

RESULTS

In total, 297 TPE and 369 MPE cases were included in this study. Over the study period, the frequency of TPE progressively declined, while that of MPE increased. In the most recent four-year period, new TPE and MPE cases with ADA levels of 40-70 IU/L occurred at comparable numbers. Multivariable analysis identified pleural fluid carcinoembryonic antigen (CEA) levels and the number of focal pleural nodules as independent predictors for MPE. Specifically, the presence of either CEA levels > 15.7 ng/mL or more than eight pleural nodules yielded the highest diagnostic accuracy with a sensitivity of 88%, specificity of 100%, and an area under the curve of 0.95.

CONCLUSION

The differential diagnosis between TPE and MPE with pleural ADA levels of 40-70 IU/L has become increasingly critical due to evolving epidemiological patterns and ADA distribution changes over time. Pleural fluid CEA levels and the characteristics of pleural nodules may offer valuable guidance in distinguishing between TPE and MPE within this diagnostic gray zone.

Unrecognized Tuberculosis: Risk Factors for Smear-Positive/Cavitary Asymptomatic Cases

Background

Screening patients with asymptomatic active tuberculosis (TB) is crucial as they can transmit the disease. Identifying the risk factors for transmission is essential for targeted screening. Understanding how the infectiousness of asymptomatic patients with TB affects disease outcomes is crucial for developing strategies to control TB spread.

Methods

We analyzed the national Korean TB cohort data to determine the factors associated with transmission risk and clinical outcomes in patients with asymptomatic pulmonary TB. The primary outcome was the factors associated with a risk factor for transmission, while the secondary outcome was mortality in asymptomatic patients with pulmonary TB stratified by transmission risk.

Results

Among 20 455 patients with pulmonary TB, 7434 (36.4%) were asymptomatic, while 1520 (25.5%) had potential transmission risks, indicated by a positive sputum acid-fast bacillus smear test or cavitation on chest radiographs. The factors associated with a higher transmission risk included male sex (odds ratio [OR], 1.385; 95% CI, 1.172-1.636; P < .001), low body mass index (BMI; OR, 1.687; 95% CI, 1.420-2.004; P < .001), current smoking (OR, 1.443; 95% CI, 1.213-1.716; P < .001), diabetes (OR, 1.399; 95% CI, 1.201-1.629; P < .001), and autoimmune disease (OR, 2.233; 95% CI, 1.295-3.850; P = .004). The mortality rate was higher in patients with a risk factor for transmission risk than in those without (9.3 vs 7.1%; P = .008).

Conclusions

Lean, smoking men with asymptomatic TB who have DM and/or autoimmune diseases have higher transmission and mortality risk. Asymptomatic populations with these risk factors warrant targeted screening.

Incidence of systemic vasculitides after Mycobacterium tuberculosis infection: a population-based cohort study in Korea

BACKGROUND

Tuberculosis (TB) is a highly prevalent disease associated with significant morbidity and mortality globally and is reported to be associated with the onset of autoimmunity. This study investigated the association between TB and the incidence of systemic vasculitides (SV).

METHODS

Data were obtained from the South Korean National Claims database to identify patients with TB and controls (who had undergone appendectomy). The overall occurrence of SV and disease subtypes during the observation period was compared between the two groups. Adjusted Cox proportional hazards regression and Kaplan-Meier analysis were performed to identify the relationship between TB and SV and to compare SV incidence.

RESULTS

We identified 418 677 patients with TB and 160 289 controls. The overall SV incidence rate was 192/1 000 000 person-years during a mean follow-up of 7.5 years and was higher in patients with TB than controls. Cox regression revealed that the risk of SV was elevated in the TB group independently (adjusted hazard ratio [aHR]: 1.72, 95% confidence interval [CI]: 1.45-2.05). Furthermore, the risk of SV was significantly higher in extrapulmonary TB (aHR: 4.28, 95% CI: 3.52-5.21) when the TB group was categorized into pulmonary and extrapulmonary TB. The findings remained identical even after applying a stabilized inverse probability of treatment weighting analysis.

CONCLUSIONS

Patients with TB have an increased risk of SV, which is prominent in extrapulmonary TB. As well as confirming TB is associated with an increased incidence of immune-related vasculitis, our findings highlight the need for clinical vigilance for early diagnosis and initiation of treatment.

Diagnostic Performance of the Modified Lung CT Screening Reporting and Data System in a TB-Endemic Country: The Korean National Lung Cancer Screening Program

BACKGROUND

In 2019, Korea initiated the world's first national low-dose CT imaging lung cancer screening (LCS) program, adapting the Lung CT Screening Reporting and Data System (Lung-RADS) to counteract the high false-positive rates driven by prevalent TB.

RESEARCH QUESTION

Does the modified Lung-RADS enhance screening specificity while maintaining sensitivity?

STUDY DESIGN AND METHODS

This nationwide, retrospective cohort study included high-risk individuals aged 54 to 74 years with active tobacco use of at least 30 pack-years participating in the national LCS program from 2019 through 2020. The modified Lung-RADS 1.0 introduced category 2b for nodules matching the size of categories 3 or 4, but showing benign features like granulomas and juxtapleural nodules, and enhanced details for category 4X. Lung cancer diagnosis rates within 1 year of screening and the diagnostic performance of the modified and original Lung-RADS were evaluated.

RESULTS

Among 152,918 participants (98.2% male; mean [SD] age, 61.7 [5.3] years), lung cancer was diagnosed in 0.68% of participants (1,047 of 152,918). A linear trend in cancer rates across Lung-RADS categories was noted (P < .001). Category 2b showed a higher cancer rate than category 2 (0.25% [45 of 18,120] vs 0.14% [33 of 23,467]; P = .01), but lower than category 3 (0.53% [37 of 7,009]; P = .001). Category 4X showed a cancer rate of 36.88% (416 of 1,128). The modified Lung-RADS demonstrated improved specificity (91.96% [139,664 of 151,871] vs 80.06% [121,589 of 151,871]; P < .001) compared with the original criteria. Although sensitivity showed a modest decrease (81.9% [858 of 1,047] vs 86.2% [903 of 1,047]; P < .001), the modification substantially reduced the follow-up burden, decreasing the number of positive screening results needed to detect 1 case of cancer from 34.5 to 15.2. The positive predictive value improved significantly (from 2.90% [903 of 31,185] to 6.57% [858 of 13,065]; P < .001), whereas the negative predictive value remained consistently high (modified, 99.86% [139,664 of 139,853] vs original, 99.88% [121,589 of 121,733]; P = .23).

INTERPRETATION

Korea's modified Lung-RADS enhanced screening efficiency through improved specificity, despite a small reduction in sensitivity.

Clinical Profiles of Multidrug-Resistant and Rifampicin-Monoresistant Tuberculosis in Korea, 2018-2021: A Nationwide Cross-Sectional Study

BACKGROUND

This study aimed to identify the clinical characteristics of multidrug-resistant/ rifampicin-resistant tuberculosis (MDR/RR-TB) in the Republic of Korea.

METHODS

Data of notified people with tuberculosis between July 2018 and December 2021 were retrieved from the Korea Tuberculosis Cohort database. MDR/RR-TB was further categorized according to isoniazid susceptibility as follows: multidrug-resistant tuberculosis (MDR-TB), rifampicin-monoresistant tuberculosis (RMR-TB), and RR-TB if susceptibility to isoniazid was unknown. Multivariable logistic regression analysis was conducted to identify the factors associated with MDR/RR-TB.

RESULTS

Between 2018 and 2021, the proportion of MDR/RR-TB cases among all TB cases and TB cases with known drug susceptibility test results was 2.1% (502/24,447). The proportions of MDR/RR-TB and MDR-TB cases among TB cases with known drug susceptibility test results were 3.3% (502/15,071) and 1.9% (292/15,071), respectively. Among all cases of rifampicin resistance, 31.7% (159/502) were RMR-TB and 10.2% (51/502) were RR-TB. Multivariable logistic regression analyses revealed that younger age, foreigners, and prior tuberculosis history were significantly associated with MDR/ RR-TB.

CONCLUSION

Rapid identification of rifampicin resistance targeting the high-risk populations, such as younger generations, foreign-born individuals, and previously treated patients are necessary for patient-centered care.

Epidemiologic characteristics and risk factors of Clostridioides difficile infection in patients with active tuberculosis in the Republic of Korea: a nationwide population-based study

BACKGROUND

The relationship between anti-tuberculosis (TB) agents and Clostridioides difficile infection (CDI) remains unclear. This study aimed to investigate the epidemiological characteristics and risk factors for CDI in patients with TB.

METHODS

This nationwide, population-based cohort study was conducted in the Republic of Korea (ROK) between January 2018 and December 2022. Data were extracted from the National Health Insurance Service-National Health Information Database. The risk factors for CDI in patients with TB were identified through multi-variate logistic regression analysis using a 1:4 greedy matching method based on age and sex.

RESULTS

During the study period, CDI developed in 2901 of the 131,950 patients with TB who were prescribed anti-TB agents. The incidence of CDI in patients with TB has increased annually in the ROK from 12.31/1000 in 2018 to 33.51/1000 in 2022. Oral metronidazole (81.94%) was the most common first-line treatment for CDI. The in-hospital mortality rate of patients with concomitant CDI and TB was 9.9%, compared with 6.9% in those with TB alone (P<0.0001). Multi-variate logistic regression analysis found intensive care unit admission, Charlson Comorbidity Index ≥3, antibiotic exposure, standard regimen, multi-drug-resistant TB and extrapulmonary TB to be significant risk factors for development of CDI in patients with TB.

CONCLUSION

CDI is uncommon in patients with TB, but it results in a significantly increased mortality rate. Patients being treated for TB should be monitored carefully for the development of CDI. Further clinical research is warranted to identify effective interventions for preventing and controlling CDI during TB treatment.

Prevalence and Characteristics of Tuberculosis in the Korean Homeless Population Based on Nationwide Tuberculosis Screening

BACKGROUND

The government of Korea implemented a strategy of prevention and early diagnosis in high-risk groups to reduce the tuberculosis (TB) burden. This study aims to investigate the TB epidemiology and gap in understanding of TB prevalence among homeless individuals by analyzing active TB chest X-ray (CXR) screening results in Korea.

METHODS

The Korean National Tuberculosis Association conducted active TB screening with CXR for homeless groups from January 1 to December 31, 2021. Sputum acid-fast bacilli smear and culture were performed for the subjects suggestive of TB on CXR. We performed a cross-sectional analysis of the data in comparison with the national health screening results from the general population.

RESULTS

Among 17,713 homeless persons, 40 (0.23%), 3,077 (17.37%), and 79 (0.45%) were categorized as suggested TB, inactive TB, and observation required, respectively. Prevalence of suggested TB in the homeless was significantly higher (3-5 fold) than in Univerthe national general health screening based on age category (p<0.005). Twenty-nine cases were confirmed as TB, yielding a prevalence of 164 cases per 100,000 individuals; 19 of these 29 cases showed inactive TB on CXR. Body mass index (p=0.0478) and CXR result (p<0.001) significantly correlated with confirmed TB based on multivariable analysis.

CONCLUSION

Nutrition status and CXR results, especially that of inactive TB, should be considered in active TB screening of the homeless population, where TB prevalence is higher than the general population.

Unilateral testicular tuberculosis in a kidney transplant recipient: a case report

Tuberculosis (TB) of the genitourinary system is a rare form of extrapulmonary TB. Testicular TB is particularly uncommon among kidney transplantation (KT) recipients. Diagnosing testicular TB is challenging due to the nonspecific nature of clinical presentations and ambiguous imaging results. In this report, we describe a case involving a 36-year-old male KT recipient who presented with left scrotal pain. He had undergone a living donor KT 8 years prior and was receiving tacrolimus, mycophenolate mofetil, and prednisolone. Laboratory tests revealed anemia, leukocytosis, and elevated inflammatory markers. Computed tomography showed left scrotal wall thickening and enlargement, suggestive of a left testicular abscess. We discontinued mycophenolate mofetil and administered intravenous antibiotics. Additionally, we performed an incision and drainage of the abscess. However, there was no improvement in his clinical course. Consequently, we performed a radical left orchiectomy. The biopsy revealed extensive chronic granulomatous inflammation with caseous necrosis, consistent with tuberculous orchiepididymitis. A quadruple anti-TB regimen was administered, leading to an improvement in the patient's condition. To the best of our knowledge, this is the first reported case of testicular TB without other organ involvement in KT recipients. Including testicular TB in the differential diagnosis of testicular infections and masses is necessary to avoid unnecessary surgical procedures.

The impact of pulmonary tuberculosis on SARS-CoV-2 infection: a nationwide cohort study

Background

The interaction between COVID-19 and tuberculosis (TB) is not yet fully understood, and large-scale research on the mortality outcome of such dual infection has been limited. This study aimed to investigate the impact of PTB on mortality among patients with COVID-19 within a Korean population by conducting an extensive analysis of a nationwide large dataset.

Method

We investigated the mortality and disease severity among COVID-19 patients who had PTB in South Korea. This study analyzed 462,444 out of 566,494 COVID-19 patients identified between January 2020 and December 2021.

Result

A total of 203 COVID-19 with PTB patients and 812 matched COVID-19 without PTB were analyzed using 1:4 propensity score matching. COVID-19 patients with PTB exhibited higher in-hospital mortality (odds ratio (OR) 3.02, 95% confidence interval (CI) 1.45-6.27, p-value = 0.003) and were at increased risk of requiring conventional oxygen therapy (OR 1.57, 95% CI 1.10-2.25, p-value = 0.013) as well as high flow nasal cannula (HFNC) or noninvasive ventilation (NIV) oxygen therapy (OR 1.91, 95 CI 1.10-3.32, p-value = 0.022) compared to those without PTB. Compared to matched COVID-19 without PTB, co-infected patients showed increased mortality rates across various timeframes, including during hospitalization, and at 30 day and 90 day intervals. In-hospital mortality rates were particularly elevated among women, individuals with malignancy, and those with lower incomes. Furthermore, the increased in-hospital mortality among PTB patients persisted irrespective of the timing of TB diagnosis or vaccination status against COVID-19.

Conclusion

We suggest that physicians be aware of the risk of mortality and severity among COVID-19 patients with PTB; coinfection with COVID-19 is a critical situation that remains to be further explored and needs more attention in countries with an intermediate to high PTB burden.

Effect of Cost-Exemption Policy on Treatment Interruption in Patients With Newly Diagnosed Pulmonary Tuberculosis in South Korea

BACKGROUND

In 2021, South Korea had the highest incidence rate (49 per 100 000 population) and the third highest mortality rate (3.8 per 100 000 population) due to pulmonary tuberculosis (TB) among Organization for Economic Co-operation and Development countries. Notably, premature interruption of TB treatment interferes with TB control efforts. Therefore, we examined the effect of the co-payment waiver on treatment interruption and mortality among patients with pulmonary TB in South Korea.

METHODS

Patients who had newly treated TB in South Korea from 2013 to 2019 were selected from the nationwide data of the entire Korean National Health Insurance Service (NHIS) population. The effects of policy implementation on treatment adherence and mortality rates depending on treatment interruption history were evaluated.

RESULTS

In total, 73 116 and 1673 patients with drug-susceptible (DS) and multidrug-resistant (MDR) pulmonary TB, respectively, were included in the final study population. After implementing the cost-exemption policy, the treatment interruption rate tended to decrease in the continuation phase in the DS-TB group (slope change: -0.097, P=.011). However, it increased in the intensive phase in the MDR-TB group (slope change: 0.733, P=.001). MDR-TB patients were likely to experience an interruption of TB treatment (adjusted odds ratio [aOR], 6.04; 95% CI, 5.43-6.71), and treatment interruption history was a significant risk factor for 1-year and overall mortality rates (adjusted hazard ratios [aHRs]: 2.01, 95% CI, 1.86-2.18 and 1.77, 95% CI, 1.70-1.84, respectively) in the DS-TB group.

CONCLUSION

Implementing the cost-exemption policy effectively reduced the treatment interruption rate among patients with DS pulmonary TB.

Effect of complicated, untreated and uncontrolled diabetes and pre-diabetes on treatment outcome among patients with pulmonary tuberculosis

BACKGROUND AND OBJECTIVE

Patients with tuberculosis and diabetes have a higher risk of unfavourable anti-tuberculosis treatment outcomes. In the present study, we aimed to evaluate the effects of various diabetes statuses on the outcomes of patients with pulmonary tuberculosis.

METHODS

Among the patients with pulmonary tuberculosis enrolled in the Korea Tuberculosis Cohort (KTBC) registry and the multicentre prospective cohort study of pulmonary tuberculosis (COSMOTB), those with diabetes and complicated diabetes were identified. The primary and secondary outcomes were unfavourable outcomes and mortality, respectively. The effect of diabetes and complicated diabetes on the outcomes was assessed using multivariable logistic regression analysis. Using COSMOTB, subgroup analyses were performed to assess the association between various diabetes statuses and outcomes.

RESULTS

In the KTBC, diabetes (adjusted odds ratio [aOR] = 1.93, 95% CI = 1.64-2.26) and complicated diabetes (aOR = 1.96, 95% CI = 1.67-2.30) were significantly associated with unfavourable outcomes, consistent with the COSMOTB data analysis. Based on subgroup analysis, untreated diabetes at baseline was an independent risk factor for unfavourable outcomes (aOR = 2.72, 95% CI = 1.26-5.61). Prediabetes and uncontrolled diabetes increased unfavourable outcomes and mortality without statistical significance.

CONCLUSION

Untreated and complicated diabetes at the time of tuberculosis diagnosis increases the risk of unfavourable outcomes and mortality.

Timing and predictors of death during treatment in patients with multidrug/rifampin-resistant tuberculosis in South Korea

BACKGROUND/AIMS

This study aimed to investigate the timing and predictors of death during treatment among patients with multidrug/rifampin-resistant tuberculosis (MDR/RR-TB) in South Korea.

METHODS

This was a retrospective cohort study that included MDR/RR-TB cases notified between 2011 and 2017 in South Korea.

RESULTS

Among 7,226 MDR/RR-TB cases, 699 (9.7%) died at a median of 167 days (IQR 51-358 d) from the initiation of MDR-TB treatment. The cumulative proportion of all-cause death was 35.5% at 90 days and 52.8% at 180 days from treatment initiation. TB-related deaths occurred at a median of 133 days (IQR 32-366 d), which was significantly earlier than the median of 184 days (IQR 68-356 d) for non-TB-related deaths (p = 0.002). In a multivariate analysis, older age was the factor most strongly associated with death, with those aged ≥ 75 years being 68 times more likely to die (aHR 68.11, 95% CI 21.75-213.26), compared those aged ≤ 24 years. In addition, male sex, comorbidities (cancer, human immunodeficiency virus, and end stage renal disease), the lowest household income class, and TB-specific factors (previous history of TB treatment, smear positivity, and fluoroquinolone resistance) were identified as independent predictors of all-cause death.

CONCLUSION

This nationwide study highlights increased deaths during the intensive phase and identifies high-risk groups including older people and those with comorbidities or socioeconomic vulnerabilities. An integrated and comprehensive strategy is required to reduce mortality in patients with MDR/RR-TB, particularly focusing on the early stages of treatment and target populations.

Influenza and the risk of active tuberculosis occurrence among individuals with latent tuberculosis infection: A national cohort study in South Korea (2015-2020)

BACKGROUND

Influenza's potential impact on active tuberculosis (TB) development has been debated, with limited clinical evidence. To address this, we explored the association between influenza episodes and TB incidence in a national cohort of individuals with latent TB infection (LTBI).

METHODS

We examined adults (≥20 years) diagnosed with LTBI between 2015 and 2020, using the Health Insurance Review and Assessment Service's national database in South Korea. We collected demographic data, comorbidities, and influenza episodes within 6 months before and after the initial LTBI diagnosis (prior vs. subsequent episode). We stratified the analysis into groups with and without TB preventive therapy (TPT).

RESULTS

Among 220,483 LTBI subjects, 49% received TPT, while 51% did not. The average age was 48.4 years, with 52% having comorbidities. A prior and subsequent influenza episode was identified in 3221 and 4580 individuals, respectively. Of these, 1159 (0.53%) developed incident TB over an average follow-up of 1.86 years. The incidence rates of TB were comparable between individuals with and without prior and/or subsequent influenza episodes in the TPT group, but 1.4 times higher in the non-TPT group for those with such episodes. Cox proportional-hazards regression analysis indicated that influenza was not a risk factor for incident TB in the TPT group. However, a subsequent influenza episode significantly increased TB risk in the non-TPT group (hazard ratio: 1.648 [95% CI, 1.053-2.580]).

CONCLUSIONS

In individuals with LTBI not receiving TPT, experiencing an influenza episode may elevate the risk of developing active TB.

Development of a multiplex droplet digital PCR method for detection and monitoring of Mycobacterium tuberculosis and drug-resistant tuberculosis

BACKGROUND

The prevalence of multidrug-resistant tuberculosis (MDR-TB) among Korean tuberculosis patients is about 4.1%, which is higher than the OECD average of 2.6%. Inadequate drug use and poor patient compliance increase MDR-TB prevalence through selective pressure. Therefore, prompt detection of drug resistance in tuberculosis patients at the time of diagnosis and quantitative monitoring of these resistant strains during treatment are crucial.

METHODS

A multiplex droplet digital PCR (ddPCR) assay was developed and assessed using DNA material of nine Mycobacterium tuberculosis strains with known mutation status that were purchased from the Korean National Tuberculosis Association. We collected a total of 18 MDR-TB residual samples referred for PCR analysis. Total DNA was extracted from the samples and subjected to the quadruplex ddPCR assay. Their results were compared to those of known resistance phenotypes.

RESULTS

The analytical sensitivity and specificity of the multiplex ddPCR assay for detecting INH, RIF, EMB, FQ, and SM resistance-causing mutations ranged from 71.43 to 100% and 94.12-100%, respectively. Follow-up sample results showed that the quadruplex ddPCR assay was sensitive enough to detect IS6110 and other mutations even after onset of treatment.

CONCLUSIONS

We developed a sensitive and accurate multiplex ddPCR assay that can detect the presence of tuberculosis quantitatively and resistance-conveying mutations concurrently. This tool could aid clinicians in the diagnosis and treatment monitoring of tuberculosis.

Incidence of tuberculosis disease in individuals diagnosed with tuberculosis infection after screening: A population-based cohort study in South Korea

OBJECTIVES

Limited evidence exists regarding the impact of adherence to diverse tuberculosis (TB) preventive therapy (TPT) regimens on TB risk in individuals with TB infections (TBIs). This study aimed to examine the association between adherence to three TPT regimens and TB incidence.

METHODS

This population-based retrospective cohort study used South Korean national health insurance data to identify individuals who were newly diagnosed with TBI between 2015 and 2020. TB incidence was compared among the different TPT regimens used. Treatment adherence was evaluated using the medication possession ratio (MPR).

RESULTS

The study involved 220,483 individuals with TBI, with half undergoing TPT. Over a mean 3.17-year follow-up, 2,430 cases of active TB were observed. TPT was associated with a 14% reduction in TB incidence risk in the entire study population with varying levels of TB risk. Non-adherence (MPR <80%) rates were 36% for 9 months of treatment with isoniazid, 22% for 4 months of treatment with rifampicin, and 18% for 3 months of treatment with isoniazid and rifampicin. Non-adherence to TPT did not lead to a decrease in the risk of TB incidence, whereas adherence to TPT (MPR ≥80%) reduced the risk of TB incidence by up to 72%.

CONCLUSIONS

This study reveals increased adherence with shorter TPT regimens in a national TBI cohort, emphasizing the pivotal role of medication adherence in preventing TB.

Population pharmacokinetic model of rifampicin for personalized tuberculosis pharmacotherapy: Effects of SLCO1B1 polymorphisms on drug exposure

BACKGROUND

Rifampicin (RIF) exhibits high pharmacokinetic (PK) variability among individuals; a low plasma concentration might result in unfavorable treatment outcomes and drug resistance. This study evaluated the contributions of non- and genetic factors to the interindividual variability of RIF exposure, then suggested initial doses for patients with different weight bands.

METHODS

This multicenter prospective cohort study in Korea analyzed demographic and clinical data, the solute carrier organic anion transporter family member 1B1 (SLCO1B1) genotypes, and RIF concentrations. Population PK modeling and simulations were conducted using nonlinear mixed-effect modeling.

RESULTS

In total, 879 tuberculosis (TB) patients were divided into a training dataset (510 patients) and a test dataset (359 patients). A one-compartment model with allometric scaling for effect of body size best described the RIF PKs. The apparent clearance (CL/F) was 16.6% higher among patients in the SLCO1B1 rs4149056 wild-type group than among patients in variant group, significantly decreasing RIF exposure in the wild-type group. The developed model showed better predictive performance compared with previously reported models. We also suggested that patients with body weights of <40 kg, 40-55 kg, 55-70 kg, and >70 kg patients receive RIF doses of 450, 600, 750, and 1050 mg/day, respectively.

CONCLUSIONS

Total body weight and SLCO1B1 rs4149056 genotypes were the most significant covariates that affected RIF CL/F variability in Korean TB patients. We suggest initial doses of RIF based on World Health Organization weight-band classifications. The model may be implemented in treatment monitoring for TB patients.

Association between diabetes mellitus and cause of death in patients with tuberculosis: A Korean nationwide cohort study

Despite its significant impact on mortality, tuberculosis (TB)-diabetes mellitus (DM) co-prevalence has not been well-elucidated for the cause of death. We investigated the impact of DM on TB-related and non-TB-related deaths in patients with TB. This retrospective nationwide cohort study included patients diagnosed with TB between 2011 and 2017 in South Korea. We performed Fine and Gray regression model analyses to assess the mortality risk of DM classified by cause of death. Of 239,848 patients, 62,435 (26.0%) had DM, and 20,203 died during anti-TB treatment. Of all deaths, 47.9% (9,668) were caused by TB, and the remaining 52.1% (10,535) was attributed to various non-TB-related causes. The mortality rate was higher in the DM than in the non-DM groups in both men and women. DM was associated with a higher risk of TB-related (adjusted hazard ratio [aHR] 1.07, 95% confidence interval [CI] 1.01-1.13) and non-TB-related (aHR 1.21, 95% CI 1.15-1.27) deaths in men; however, only a higher risk of non-TB-related deaths (aHR 1.29, 95% CI 1.20-1.38) in women. Our findings indicate that DM is independently associated with a greater risk of death during anti-TB treatment among patients with TB for both TB-related and non-TB-related deaths.

Do patients attempt and succeed in quitting smoking during tuberculosis treatment? A prospective cohort study

BACKGROUND

Despite a well-known relation between smoking tobacco and the tuberculosis epidemic, the factors associated with smoking cessation in tuberculosis patients are unclear. This study aims to examine the cascade of smoking cessation and the factors associated with persistent smoking among tuberculosis patients.

METHODS

We conducted a prospective cohort study enrolling adult patients with pulmonary tuberculosis between 2016 and 2019 in the Republic of Korea. We examined the smoking status at baseline, followed the current smokers, re-examined their smoking status after 6 months of anti-tuberculosis treatment, and identified the factors associated with persistent smoking.

RESULTS

Of the 419 enrolled patients, 109 (26.0%) were current smokers at baseline. Of the 79 current smokers who completed the 6-month survey, 24 (30.4%) succeeded in quitting smoking after 6 months of treatment. The adjusted odds ratio for persistent smoking was 6.57 (95% confidence interval [CI], 1.76-27.83) for drinking and 0.15 (95% CI, 0.03-0.68) for diabetes comorbidity.

CONCLUSION

Drinking alcohol and diabetes comorbidity were important factors in smoking cessation. Only one third of the tuberculosis patients in our study cohort succeeded in quitting smoking during the 6-month treatment period. More aggressive interventions for smoking cessation should be adopted within the national anti-tuberculosis program.

Risk of loss to follow-up among tuberculosis patients in South Korea: whom should we focus on?

Introduction

In South Korea, public-private mix (PPM) has been a key strategy in national tuberculosis (TB) control program. This study aimed to identify rate of loss to follow-up (LTFU) among TB patients in nationwide PPM institutions and their risk factors.

Methods

A nationwide prospective observational study including drug susceptible TB patients diagnosed from the 1st day to the 10th day of every month between July 2018 and December 2020 in PPM institutions was designed. Multivariable survival models in which death and failure were designated as events with competing risk were used to investigate risk factors for LTFU.

Results

A total of 14,942 patients were included. Of them, 356 (2.4%) had an LTFU. Risk factors for LTFU were: underweight patients (adjusted hazard ratio (aHR): 1.47, 95% CI: 1.12-1.92), patients living alone (aHR: 1.43, 95% CI: 1.16-1.76), heavy drinkers (aHR: 1.67, 95% CI: 1.16-2.39), those with malignancy (aHR: 1.49, 95% CI: 1.07-2.05), foreigners (aHR: 5.96, 95% CI: 4.51-7.89), and those with previous TB history reported as an unfavorable outcome (aHR: 4.43, 95% CI: 2.77-7.08). Effect of age on LTFU was not significant. Brief interruption of anti-TB treatment (less than two months) in current session was associated with subsequent LTFU [adjusted odds ratio: 13.09 (10.29-16.66)].

Conclusion

Identifying vulnerability of patients such as living alone, being heavy alcoholics, being foreigners or having previous TB history reported as an unfavorable outcome is required. Thorough case management for these vulnerable groups could be feasible with collaboration between public and private sectors.

Effects of underweight and overweight on mortality in patients with pulmonary tuberculosis

Background

Poor nutrition increases disease severity and mortality in patients with tuberculosis (TB). There are gaps in our understanding of the effects of being underweight or overweight on TB in relation to sex.

Methods

We generated a nationwide TB registry database and assessed the effects of body mass index (BMI) on mortality in patients with pulmonary TB. The cause of death was further classified as TB-related or non-TB-related deaths. First, logistic regression analysis was performed to assess the association between BMI (a continuous variable) and mortality, and subgroup analyses of the multivariable logistic regression model were performed separately in male and female patients. Second, we categorized BMI into three groups: underweight, normal weight, and overweight, and assessed the impact of being underweight or overweight on mortality with reference to normal weight.

Results

Among 9,721 patients with pulmonary TB, the mean BMI was 21.3 ± 3.4; 1,927 (19.8%) were underweight, and 2,829 (29.1%) were overweight. In multivariable logistic regression analysis, mortality was significantly increased with the decrement of BMI (adjusted odds ratio [aOR] = 0.893, 95% confidence interval [CI] = 0.875-0.911). In subgroup analyses, underweight patients had significantly higher odds of mortality, especially TB-related deaths (aOR = 2.057, 95% CI = 1.546-2.735). The association with mortality and male patients was higher (aOR = 2.078, 95% CI = 1.717-2.514), compared with female patients (aOR = 1.724, 95% CI = 1.332-2.231). Being overweight had a significant protective effect against TB-related death only in females (aOR = 0.500, 95% CI = 0.268-0.934), whereas its effect on non-TB-related death was observed only in males (aOR = 0.739, 95% CI = 0.587-0.930).

Conclusion

Being underweight was linked to high mortality, whereas being overweight had beneficial effects in patients with pulmonary TB.

Metabolic Disorders Are Associated With Drug-Induced Liver Injury During Antituberculosis Treatment: A Multicenter Prospective Observational Cohort Study in Korea

Background

Drug-induced liver injury (DILI) may lead to the discontinuation of antituberculosis (anti-TB) treatment (ATT). Some studies have suggested that metabolic disorders increase the risk of DILI during ATT. This study aimed to identify risk factors for DILI, particularly metabolic disorders, during ATT.

Methods

A multicenter prospective observational cohort study to evaluate adverse events during ATT was conducted in Korea from 2019 to 2021. Drug-susceptible patients with TB who had been treated with standard ATT for 6 months were included. The patients were divided into 2 groups depending on the presence of 1 or more metabolic conditions, such as insulin resistance, hypertension, obesity, and dyslipidemia. We monitored ATT-related adverse events, including DILI, and treatment outcomes. The incidence of DILI was compared between individuals with and without metabolic disorders, and related factors were evaluated.

Results

Of 684 patients, 52 (7.6%) experienced DILI, and 92.9% of them had metabolic disorders. In the multivariable analyses, underlying metabolic disorders (adjusted hazard ratio [aHR], 2.85; 95% CI, 1.01-8.07) and serum albumin <3.5 g/dL (aHR, 2.26; 95% CI, 1.29-3.96) were risk factors for DILI during ATT. In the 1-month landmark analyses, metabolic disorders were linked to an elevated risk of DILI, especially significant alanine aminotransferase elevation. The treatment outcome was not affected by the presence of metabolic disorders.

Conclusions

Patients with metabolic disorders have an increased risk of ATT-induced liver injury compared with controls. The presence of metabolic disorders and hypoalbuminemia adversely affects the liver in patients with ATT.

Development of a population pharmacokinetic model of pyrazinamide to guide personalized therapy: impacts of geriatric and diabetes mellitus on clearance

Objectives: This study was performed to develop a population pharmacokinetic model of pyrazinamide for Korean tuberculosis (TB) patients and to explore and identify the influence of demographic and clinical factors, especially geriatric diabetes mellitus (DM), on the pharmacokinetics (PK) of pyrazinamide (PZA). Methods: PZA concentrations at random post-dose points, demographic characteristics, and clinical information were collected in a multicenter prospective TB cohort study from 18 hospitals in Korea. Data obtained from 610 TB patients were divided into training and test datasets at a 4:1 ratio. A population PK model was developed using a nonlinear mixed-effects method. Results: A one-compartment model with allometric scaling for body size effect adequately described the PK of PZA. Geriatric patients with DM (age >70 years) were identified as a significant covariate, increasing the apparent clearance of PZA by 30% (geriatric patients with DM: 5.73 L/h; others: 4.50 L/h), thereby decreasing the area under the concentration-time curve from 0 to 24 h by a similar degree compared with other patients (geriatric patients with DM: 99.87 μg h/mL; others: 132.3 μg h/mL). Our model was externally evaluated using the test set and provided better predictive performance compared with the previously published model. Conclusion: The established population PK model sufficiently described the PK of PZA in Korean TB patients. Our model will be useful in therapeutic drug monitoring to provide dose optimization of PZA, particularly for geriatric patients with DM and TB.

Differential effects of sex on tuberculosis location and severity across the lifespan

Disparities exist between sexes regarding tuberculosis (TB) incidence, as well as disease severity and outcome. Using a nationwide TB registry database, we explored the impact of sex and age on extrapulmonary TB (EPTB) among all enrolled patients by (1) calculating the female proportion for every age category according to TB-affected locations, (2) calculating the proportions of EPTB stratified by sex according to age, (3) conducting multivariable analysis to examine the impact of sex and age on EPTB likelihood, and (4) assessing the odds of EPTB for female compared to male as reference in every age category. Further, we explored the impact of sex and age on disease severity among pulmonary TB (PTB) patients. Of all the TB patients, 40.1% were female, with a male-to-female ratio of 1.49. The proportion of females was lowest in their fifties, resembling a U-shape. The male-to-female ratios in PTB and EPTB were 1.67 and 1.03, respectively. Compared to men, women were significantly associated with EPTB in their forties, fifties, and sixties. Female patients with PTB had significantly lower odds of having cavitation and positive smear test results in their fifties. Significant differences were found concerning TB location and severity between sexes, especially during reproductive age.