Persistent latent tuberculosis reactivation risk in United States immigrants

Multiple cytokine analysis based on QuantiFERON-TB gold plus in different tuberculosis infection status: an exploratory study

BACKGROUND

More efficient and convenient diagnostic method is a desperate need to reduce the burden of tuberculosis (TB). This study explores the multiple cytokines secretion based on QuantiFERON-TB Gold Plus (QFT-Plus), and screens for optimal cytokines with diagnostic potential to differentiate TB infection status.

METHODS

Twenty active tuberculosis (ATB) patients, fifteen patients with latent TB infection (LTBI), ten patients with previous TB and ten healthy controls (HC) were enrolled. Whole blood samples were collected and stimulated by QFT-Plus TB1 and TB2 antigens. The levels of IFN-γ, TNF-α, IL-2, IL-6, IL-5, IL-10, IP-10, IL-1Ra, CXCL-1 and MCP-1 in supernatant were measured by Luminex bead-based multiplex assays. The receiver operating characteristic curve was used to evaluate the diagnostic accuracy of cytokine for distinguishing different TB infection status.

RESULTS

After stimulation with QFT-Plus TB1 and TB2 antigens, the levels of all cytokines, except IL-5 in TB2 tube, in ATB group were significantly higher than that in HC group. The levels of IL-1Ra concurrently showed the equally highest AUC for distinguishing TB infection from HC, followed by the levels of IP-10 in both TB1 tube and TB2 tube. Moreover, IP-10 levels displayed the largest AUC for distinguishing ATB patients from non-ATB patients. Meanwhile, the levels of IP-10 also demonstrated the largest AUC in both TB1 tube and TB2 tube for distinguishing ATB patients from LTBI.

CONCLUSIONS

In addition to conventional detection of IFN-γ, measuring IP-10 and IL-1Ra based on QFT-Plus may have the more tremendous potential to discriminate different TB infection status.

Trends in tuberculosis clinicians' adoption of short-course regimens for latent tuberculosis infection

Objective

Little is known about regimen choice for latent tuberculosis infection in the United States. Since 2011, the Centers for Disease Control and Prevention has recommended shorter regimens-12 weeks of isoniazid and rifapentine or 4 months of rifampin-because they have similar efficacy, better tolerability, and higher treatment completion than 6-9 months of isoniazid. The objective of this analysis is to describe frequencies of latent tuberculosis infection regimens prescribed in the United States and assess changes over time.

Methods

Persons at high risk for latent tuberculosis infection or progression to tuberculosis disease were enrolled into an observational cohort study from September 2012-May 2017, tested for tuberculosis infection, and followed for 24 months. This analysis included those with at least one positive test who started treatment.

Results

Frequencies of latent tuberculosis infection regimens and 95% confidence intervals were calculated overall and by important risk groups. Changes in the frequencies of regimens by quarter were assessed using the Mann-Kendall statistic. Of 20,220 participants, 4,068 had at least one positive test and started treatment: 95% non-U.S.-born, 46% female, 12% <15 years old. Most received 4 months of rifampin (49%), 6-9 months of isoniazid (32%), or 12 weeks of isoniazid and rifapentine (13%). Selection of short-course regimens increased from 55% in 2013 to 81% in late 2016 (p < 0.001).

Conclusions

Our study identified a trend towards adoption of shorter regimens. Future studies should assess the impact of updated treatment guidelines, which have added 3 months of daily isoniazid and rifampin to recommended regimens.

Construction and Validation of a Diagnostic Scoring System for Predicting Active Pulmonary Tuberculosis in Patients with Positive T-SPOT Based on Indicators Associated with Coagulation and Inflammation: A Retrospective Cross-Sectional Study

Introduction

Tuberculosis (TB) is a life-threatening single infectious disease, which remains a major global public health concern. This study was to establish and validate a clinically practical diagnostic scoring system for predicting active pulmonary tuberculosis (APTB) in patients with positive tuberculosis T cell spot test [T-SPOT] using indicators associated with coagulation and inflammation.

Methods

A single-center retrospective cross-sectional study was performed to include patients with positive T-SOPT registered and hospitalized at Wuhan Jinyintan Hospital between January 2017 and December 2019. All patients were separated into the active pulmonary tuberculosis (APTB) group and the inactive pulmonary tuberculosis (IPTB) group, according to the diagnostic criteria from China's Expert Consensus for APTB and IPTB. Subsequently, the patients were randomized into a training set and a validation set at a ratio of 2:1. Indicators associated with coagulation and inflammation, including prothrombin time activity (PTA), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen concentration (Fbg-C), C-reactive protein/albumin ratio (CAR), C-reactive protein/prealbumin ratio (CPR), neutrophils count/lymphocyte count ratio (NLR), platelet count/lymphocyte count ratio (PLR), monocyte count/lymphocyte count ratio (MLR), and erythrocyte sedimentation rate (ESR) were obtained from electronic medical record system (EMRS). Stepwise logistic regression was performed in the training set to build a diagnostic model for predicting APTB, which was transformed into an easily applicable scoring system via nomogram. Receiver operating characteristic (ROC) analysis, calibration curve (CC), and decision curve analysis (DCA) were conducted to evaluate the predictive performance of the established diagnostic scoring system.

Results

A total of 508 patients [training set (211 cases of APTB and 116 cases of IPTB) and validation set (103 cases of APTB and 78 cases of IPTB)] with positive T-SPOT were recruited in the study. Stepwise logistic regression showed that CPR, MLR, ESR, APTT and Fbg-C were independent predictors for APTB. The scoring system was subsequently formulated based on the abovementioned predictors, which correspond to scores of 10, 6, 7, 5, and 5, respectively. In addition, patients are more likely to be diagnosed as APTB when the cut-off score was ≥16 scores, while patients with <16 scores are more likely to be diagnosed as IPTB. The scoring system showed good predictive efficacy in both the training set [area under the curve (AUC): 0.887] and the validation set (AUC: 0.898). Furthermore, both CC and DCA confirmed the clinical utility of the scoring system.

Conclusion

The data suggest that the combination of indicators associated with coagulation and inflammation could serve as biomarkers to identify APTB in patients with positive T-SPOT. In addition, patients with positive T-SPOT were more prone to be diagnosed with APTB when having a combined total of scores ≥16 in the scoring system.

Health economic analyses of latent tuberculosis infection screening and preventive treatment among people living with HIV in lower tuberculosis incidence settings: a systematic review

Introduction: In lower tuberculosis (TB) incidence countries (<100 cases/100,000/year), screening and preventive treatment (PT) for latent TB infection (LTBI) among people living with HIV (PLWH) is often recommended, yet guidelines advising which groups to prioritise for screening can be contradictory and implementation patchy. Evidence of LTBI screening cost-effectiveness may improve uptake and health outcomes at reasonable cost. Methods: Our systematic review assessed cost-effectiveness estimates of LTBI screening/PT strategies among PLWH in lower TB incidence countries to identify model-driving inputs and methodological differences. Databases were searched 1980-2020. Studies including health economic evaluation of LTBI screening of PLWH in lower TB incidence countries (<100 cases/100,000/year) were included. Results: Of 2,644 articles screened, nine studies were included. Cost-effectiveness estimates of LTBI screening/PT for PLWH varied widely, with universal screening/PT found highly cost-effective by some studies, while only targeting to high-risk groups (such as those from mid/high TB incidence countries) deemed cost-effective by others. Cost-effectiveness of strategies screening all PLWH from studies published in the past five years varied from US$2828 to US$144,929/quality-adjusted life-year gained (2018 prices). Study quality varied, with inconsistent reporting of methods and results limiting comparability of studies. Cost-effectiveness varied markedly by screening guideline, with British HIV Association guidelines more cost-effective than NICE guidelines in the UK. Discussion: Cost-effectiveness studies of LTBI screening/PT for PLWH in lower TB incidence settings are scarce, with large variations in methods and assumptions used, target populations and screening/PT strategies evaluated. The limited evidence suggests LTBI screening/PT may be cost-effective for some PLWH groups but further research is required, particularly on strategies targeting screening/PT to PLWH at higher risk. Standardisation of model descriptions and results reporting could facilitate reliable comparisons between studies, particularly to identify those factors driving the wide disparity between cost-effectiveness estimates. Registration: PROSPERO CRD42020166338 (18/03/2020).

A scoring system developed from a nomogram to differentiate active pulmonary tuberculosis from inactive pulmonary tuberculosis

Purpose

This study aimed to develop and validate a scoring system based on a nomogram of common clinical metrics to discriminate between active pulmonary tuberculosis (APTB) and inactive pulmonary tuberculosis (IPTB).

Patients and methods

A total of 1096 patients with pulmonary tuberculosis (PTB) admitted to Wuhan Jinyintan Hospital between January 2017 and December 2019 were included in this study. Of these patients with PTB, 744 were included in the training cohort (70%; 458 patients with APTB, and 286 patients with IPTB), and 352 were included in the validation cohort (30%; 220 patients with APTB, and 132 patients with IPTB). Data from 744 patients from the training cohort were used to establish the diagnostic model. Routine blood examination indices and biochemical indicators were collected to construct a diagnostic model using the nomogram, which was then transformed into a scoring system. Furthermore, data from 352 patients from the validation cohort were used to validate the scoring system.

Results

Six variables were selected to construct the prediction model. In the scoring system, the mean corpuscular volume, erythrocyte sedimentation rate, albumin level, adenosine deaminase level, monocyte-to-high-density lipoprotein ratio, and high-sensitivity C-reactive protein-to-lymphocyte ratio were 6, 4, 7, 5, 5, and 10, respectively. When the cut-off value was 15.5, the scoring system for recognizing APTB and IPTB exhibited excellent diagnostic performance. The area under the curve, specificity, and sensitivity of the training cohort were 0.919, 84.06%, and 86.36%, respectively, whereas those of the validation cohort were 0.900, 82.73, and 86.36%, respectively.

Conclusion

This study successfully constructed a scoring system for distinguishing APTB from IPTB that performed well.

Demographic Control Measure Implications of Tuberculosis Infection for Migrant Workers across Taiwan Regions

A sharp increase in migrant workers has raised concerns for TB epidemics, yet optimal TB control strategies remain unclear in Taiwan regions. This study assessed intervention efforts on reducing tuberculosis (TB) infection among migrant workers. We performed large-scale data analyses and used them to develop a control-based migrant worker-associated susceptible-latently infected-infectious-recovered (SLTR) model. We used the SLTR model to assess potential intervention strategies such as social distancing, early screening, and directly observed treatment, short-course (DOTS) for TB transmission among migrant workers and locals in three major hotspot cities from 2018 to 2023. We showed that social distancing was the best single strategy, while the best dual measure was social distancing coupled with early screening. However, the effectiveness of the triple strategy was marginally (1-3%) better than that of the dual measure. Our study provides a mechanistic framework to facilitate understanding of TB transmission dynamics between locals and migrant workers and to recommend better prevention strategies in anticipation of achieving WHO's milestones by the next decade. Our work has implications for migrant worker-associated TB infection prevention on a global scale and provides a knowledge base for exploring how outcomes can be best implemented by alternative control measure approaches.

Association between Birth Region and Time to Tuberculosis Diagnosis among Non-US-Born Persons in the United States

Approximately 90% of tuberculosis (TB) cases among non–US-born persons in the United States are attributable to progression of latent TB infection to TB disease. Using survival analysis, we investigated whether birthplace is associated with time to disease progression among non–US-born persons in whom TB disease developed. We derived a Cox regression model comparing differences in time to TB diagnosis after US entry among 19 birth regions, adjusting for sex, birth year, and age at entry. After adjusting for age at entry and birth year, the median time to TB diagnosis was lowest among persons from Middle Africa, 128 months (95% CI 116–146 months) for male persons and 121 months (95% CI 108–136 months) for female persons. We found time to TB diagnosis among non–US-born persons varied by birth region, which represents a prognostic indicator for progression of latent TB infection to TB disease.

Cost-effectiveness of the latent tuberculosis screening program for migrants in Stockholm Region

INTRODUCTION

The majority of tuberculosis (TB) cases in Sweden occur among migrants from endemic countries through activation of latent tuberculosis infection (LTBI). Sweden has LTBI-screening policies for migrants that have not been previously evaluated. This study aimed to assess the cost-effectiveness of the current screening strategy in Stockholm.

METHODS

A Markov model was developed to predict the costs and effects of the current LTBI-screening program compared to a scenario of no LTBI screening over a 50-year time horizon. Epidemiological and cost data were obtained from local sources when available. The primary outcomes were incremental cost-effectiveness ratio (ICER) in terms of societal cost per quality-adjusted life year (QALY).

RESULTS

Screening migrants in the age group 13-19 years had the lowest ICER, 300,082 Swedish Kronor (SEK)/QALY, which is considered cost-effective in Sweden. In the age group 20-34, ICER was 714,527 SEK/QALY (moderately cost-effectives) and in all age groups above 34 ICERs were above 1,000,000 SEK/QALY (not cost-effective). ICER decreased with increasing TB incidence in country of origin.

CONCLUSION

Screening is cost-effective for young cohorts, mainly between 13 and 19, while cost-effectiveness in age group 20-34 years could be enhanced by focusing on migrants from highest incidence countries and/or by increasing the LTBI treatment initiation rate. Screening is not cost-effective in older cohorts regardless of the country of origin.

US Tuberculosis Rates among Persons Born Outside the United States Compared with Rates in Their Countries of Birth, 2012-20161

The US Centers for Disease Control and Prevention recommends screening populations at increased risk for tuberculosis (TB), including persons born in countries with high TB rates. This approach assumes that TB risk for expatriates living in the United States is representative of TB risk in their countries of birth. We compared US TB rates by country of birth with corresponding country rates by calculating incidence rate ratios (IRRs) (World Health Organization rate/US rate). The median IRR was 5.4. The median IRR was 0.5 for persons who received a TB diagnosis <1 year after US entry, 4.9 at 1 to <10 years, and 10.0 at >10 years. Our analysis suggests that World Health Organization TB rates are not representative of TB risk among expatriates in the United States and that TB testing prioritization in the United States might better be based on US rates by country of birth and years in the United States.

Estimating Long-term Tuberculosis Reactivation Rates in Australian Migrants

BACKGROUND

The risk of progression to tuberculosis (TB) disease is greatest soon after infection, yet disease may occur many years or decades later. However, rates of TB reactivation long after infection remain poorly quantified. Australia has a low incidence of TB and most cases occur among migrants. We explored how TB rates in Australian migrants varied with time from migration, age, and gender.

METHODS

We combined TB notifications in census years 2006, 2011, and 2016 with time- and country-specific estimates of latent TB prevalences in migrant cohorts to quantify postmigration reactivation rates.

RESULTS

During the census years, 3246 TB cases occurred among an estimated 2 084 000 migrants with latent TB. There were consistent trends in postmigration reactivation rates, which appeared to be dependent on both time from migration and age. Rates were lower in cohorts with increasing time, until at least 20 years from migration, and on this background there also appeared to be increasing rates during youth (15-24 years of age) and in those aged 70 years and above. Within 5 years of migration, annual reactivation rates were approximately 400 per 100 000 (uncertainty interval [UI] 320-480), dropping to 170 (UI 130-220) from 5 to 10 years and 110 (UI 70-160) from 10 to 20 years, then sustaining at 60-70 per 100 000 up to 60 years from migration. Rates varied depending on age at migration.

CONCLUSIONS

Postmigration reactivation rates appeared to show dependency on both time from migration and age. This approach to quantifying reactivation risks will enable evaluations of the potential impacts of TB control and elimination strategies.

Assessing Complexity Among Patients With Tuberculosis in California, 1993-2016

Background

Although the number of patients with active tuberculosis (TB) has decreased in the last 25 years, anecdotal reports suggest that the complexity of these patients has increased. However, this complexity and its components have never been quantified or defined. We therefore aimed to describe the complexity of patients with active TB in California during 1993–2016.

Methods

We analyzed data on patient comorbidities, clinical features, and demographics from the California Department of Public Health TB Registry. All adult patients who were alive at the time of TB diagnosis in California during 1993–2016 were included in the analyses. Factors deemed by an expert panel to increase complexity (ie, increased resources or expertise requirement for successful management) were analyzed and included the following: age >75 years, HIV infection, multidrug resistance (MDR), and extrapulmonary TB disease. Second, using additional information on other comorbidities available starting in 2010, we performed exploratory factor analysis on 25 variables in order to define the dimensions of complexity.

Results

Among the 67512 patients analyzed, the proportion of patients with extrapulmonary disease, age >75 years, or MDR-TB each increased over the study period (P < .001), while the proportion of patients with HIV decreased. Furthermore, the proportion of patients with at least 1 factor of those increased, rising from 38.8% to 45.3% (P < .001) from 1993 to 2016. Dimensions of complexity identified in the exploratory factor analysis included the following: race/immigration, social features, elderly/institutionalized, advanced TB, comorbidity, and drug resistance risk.

Conclusions

In this first description of complexity in the setting of TB, we found that the complexity of patients with active TB has risen over the last 25 years in California. These findings suggest that despite the overall decline in active TB cases, effective management of more complex patients may require additional attention and resource investment.

Gaps in the care cascade for screening and treatment of refugees with tuberculosis infection in Middle Tennessee: a retrospective cohort study

BACKGROUND

Treatment of tuberculosis infection (TBI) in individuals at high risk for tuberculosis (TB) disease is a priority for TB elimination in the US. Newly arrived refugees in Middle Tennessee are screened for TBI, but factors associated with gaps in the TBI care cascade are not well characterized.

METHODS

We assessed the TBI care cascade from US entry to completion of treatment for refugees who resettled in Middle Tennessee from 2012 through 2016. We assessed factors associated with treatment initiation and completion using logistic regression models.

RESULTS

Of 6776 refugees who completed initial health screening, 1681 (25%) screened positive for TBI, 1208 were eligible for treatment, 690 started treatment, and 432 completed treatment. Male sex (Odds Ratio [OR]: 1.42; 95% Confidence Interval [CI]: 1.06, 1.89) and screening with interferon gamma release assay compared to tuberculin skin test (OR: 2.89; 95% CI: 1.59, 5.27) were associated with increased treatment initiation; living farther away from TB clinic was associated with decreased treatment initiation (OR: 0.91; 95% CI: 0.83, 0.99). Existing diabetes (OR: 7.27; 95% CI: 1.93, 27.30), receipt of influenza vaccination (OR: 1.65; 95% CI: 1.14, 2.40) and region of origin from South-Eastern or Southern Asia (ORSEAsia: 2.30; 95% CI: 1.43, 3.70; ORSAsia: 1.64; 95% CI: 1.02, 2.64) were associated with increased treatment completion. Six refugees developed TB disease after declining (n = 4) or partially completing (n = 2) TBI treatment; none who completed treatment developed TB disease.

CONCLUSIONS

We determined gaps in the TBI care cascade among refugees in Middle Tennessee. Further assessment of barriers to treatment initiation and completion and interventions to assist refugees are warranted to improve these gaps and prevent TB disease.

Tuberculosis among Newly Arrived Immigrants and Refugees in the United States

Rationale: U.S. health departments routinely conduct post-arrival evaluation of immigrants and refugees at risk for tuberculosis (TB), but this important intervention has not been thoroughly studied.Objectives: To assess outcomes of the post-arrival evaluation intervention.Methods: We categorized at-risk immigrants and refugees as having had recent completion of treatment for pulmonary TB disease overseas (including in Mexico and Canada); as having suspected TB disease (chest radiograph/clinical symptoms suggestive of TB) but negative culture results overseas; or as having latent TB infection (LTBI) diagnosed overseas. Among 2.1 million U.S.-bound immigrants and refugees screened for TB overseas during 2013-2016, 90,737 were identified as at risk for TB. We analyzed a national data set of these at-risk immigrants and refugees and calculated rates of TB disease for those who completed post-arrival evaluation.Results: Among 4,225 persons with recent completion of treatment for pulmonary TB disease overseas, 3,005 (71.1%) completed post-arrival evaluation within 1 year of arrival; of these, TB disease was diagnosed in 22 (732 cases/100,000 persons), including 4 sputum culture-positive cases (133 cases/100,000 persons), 13 sputum culture-negative cases (433 cases/100,000 persons), and 5 cases with no reported sputum-culture results (166 cases/100,000 persons). Among 55,938 with suspected TB disease but negative culture results overseas, 37,089 (66.3%) completed post-arrival evaluation; of these, TB disease was diagnosed in 597 (1,610 cases/100,000 persons), including 262 sputum culture-positive cases (706 cases/100,000 persons), 281 sputum culture-negative cases (758 cases/100,000 persons), and 54 cases with no reported sputum-culture results (146 cases/100,000 persons). Among 30,574 with LTBI diagnosed overseas, 18,466 (60.4%) completed post-arrival evaluation; of these, TB disease was diagnosed in 48 (260 cases/100,000 persons), including 11 sputum culture-positive cases (60 cases/100,000 persons), 22 sputum culture-negative cases (119 cases/100,000 persons), and 15 cases with no reported sputum-culture results (81 cases/100,000 persons). Of 21,714 persons for whom treatment for LTBI was recommended at post-arrival evaluation, 14,977 (69.0%) initiated treatment and 8,695 (40.0%) completed treatment.Conclusions: Post-arrival evaluation of at-risk immigrants and refugees can be highly effective. To optimize the yield and impact of this intervention, strategies are needed to improve completion rates of post-arrival evaluation and treatment for LTBI.

Screening for infection in unaccompanied asylum-seeking children and young people

We aimed to evaluate a screening programme for infection in unaccompanied asylum seeking children and young people against national guidance and to described the rates of identified infection in the cohort. The audit was conducted by retrospective case note review of routinely collected, anonymised patient data from all UASC referred between January 2016 and December 2018 in two paediatric infectious diseases clinics.There were 252 individuals from 19 countries included in the study, of these 88% were male, and the median age was 17 years (range 11-18). Individuals from Afghanistan, Eritrea and Albania constituted the majority of those seen. Median time between arriving in the UK and infection screening was 6 months (IQR 4-10 months, data available on 197 UASC). There were 94% (238/252) of cases tested for tuberculosis (TB), of whom 23% (55/238) were positive, including three young people with TB disease. Of those tested for hepatitis B, 4.8% (10/210) were positive, 0.5% (1/121) were positive for hepatitis C and of 252 tested, none were positive for HIV. Of the 163 individuals who were tested for schistosomiasis, 27 were positive (16%).The majority of patients were appropriately tested for infections with a high rate of identification of treatable asymptomatic infection. Infections were of both individual and public health significance. Our findings of clinically significant rates of treatable infections in UASC highlight the importance of infection screening for all in this vulnerable patient group.

Higher Rates of Tuberculosis Among Class B1 Filipino Immigrants to Hawaii Compared to Nationwide, 2010-2014

BACKGROUND

Immigrants to the United States from countries with a high burden of tuberculosis (TB) who have abnormal chest radiographs but negative sputum cultures during pre-immigration screening (TB Class B1) have a high risk of being diagnosed with TB disease within 1 year of arrival.

METHODS

Using 2010-2014 national surveillance data, we compared proportions of Class B1 Filipino immigrants who received a diagnosis of TB disease within 1 year of arrival to Hawaii to proportions in other U.S. states (not including Hawaii) using chi-squared tests.

RESULTS

In Hawaii, 40/1190 (3.4%) of Class B1 Filipino immigrants to Hawaii received a diagnosis of TB disease within 1 year of arrival compared with 220/16,035 (1.4%) nationwide (P < .01).

CONCLUSIONS

During 2010-2014, the percentage of recent Class B1 Filipino immigrants in Hawaii with TB disease diagnosed within 1 year of arrival was over twice that as nationwide.

Cost-effectiveness of Latent Tuberculosis Infection Screening before Immigration to Low-Incidence Countries

Prospective migrants to countries where the incidence of tuberculosis (TB) is low (low-incidence countries) receive TB screening; however, screening for latent TB infection (LTBI) before immigration is rare. We evaluated the cost-effectiveness of mandated and sponsored preimmigration LTBI screening for migrants to low-incidence countries. We used discrete event simulation to model preimmigration LTBI screening coupled with postarrival follow-up and treatment for those who test positive. Preimmigration interferon-gamma release assay screening and postarrival rifampin treatment was preferred in deterministic analysis. We calculated cost per quality-adjusted life-year gained for migrants from countries with different TB incidences. Our analysis provides evidence of the cost-effectiveness of preimmigration LTBI screening for migrants to low-incidence countries. Coupled with research on sustainability, acceptability, and program implementation, these results can inform policy decisions.

Comparing QuantiFERON-TB Gold Plus with Other Tests To Diagnose Mycobacterium tuberculosis Infection

The fourth-generation QuantiFERON test for tuberculosis infection, QuantiFERON-TB Gold Plus (QFT-Plus) has replaced the earlier version, QuantiFERON-TB Gold In-Tube (QFT-GIT). A clinical need exists for information about agreement between QFT-Plus and other tests. We conducted this study to assess agreement of test results for QFT-Plus with those of QuantiFERON-TB Gold In-Tube (QFT-GIT), T-SPOT.TB (T-SPOT), and the tuberculin skin test (TST). Persons at high risk of latent tuberculosis infection (LTBI) and/or progression to tuberculosis (TB) disease were enrolled at the 10 sites of the Tuberculosis Epidemiologic Studies Consortium from October 2016 through May 2017; each participant received all four tests. Cohen's kappa (κ) and Wilcoxon signed-rank test compared qualitative and quantitative results of QFT-Plus with the other tests. Test results for 506 participants showed 94% agreement between QFT-Plus and QFT-GIT, with 19% positive and 75% negative results. When the tests disagreed, it was most often in the direction of QFT-GIT negative/QFT-Plus positive. QFT-Plus had similar concordance as QFT-GIT with TST (77% and 77%, respectively) and T-SPOT (92% and 91%, respectively). The study showed high agreement between QFT-GIT and QFT-Plus in a direct comparison. Both tests had similar agreement with TST and T-SPOT.

The impact of migration on tuberculosis in the United States

Due to greater exposure to Mycobacterium tuberculosis infection before migration, migrants moving to low-incidence settings can experience substantially higher tuberculosis (TB) rates than the native-born population. This review describes the impact of migration on TB epidemiology in the United States, and how the TB burden differs between US-born and non-US-born populations. The United States has a long history of receiving migrants from other parts of the world, and TB among non-US-born individuals now represents the majority of new TB cases. Based on an analysis of TB cases among individuals from the top 30 countries of origin in terms of non-US-born TB burden between 2003 and 2015, we describe how TB risks vary within the non-US-born population according to age, years since entry, entry year, and country of origin. Variation along each of these dimensions is associated with more than 10-fold differences in the risk of developing active TB, and this risk is also positively associated with TB incidence estimates for the country of origin and the composition of the migrant pool in the entry year. Approximately 87 000 lifetime TB cases are predicted for the non-US-born population resident in the United States in 2015, and 5800 lifetime cases for the population entering the United States in 2015.

Demographic predictors of active tuberculosis in people migrating to British Columbia, Canada: a retrospective cohort study

BACKGROUND

Canadian tuberculosis (TB) guidelines recommend targeting postlanding screening for and treatment of latent tuberculosis infection (LTBI) in people migrating to Canada who are at increased risk for TB reactivation. Our objectives were to calculate robust longitudinal estimates of TB incidence in a cohort of people migrating to British Columbia, Canada, over a 29-year period, and to identify groups at highest risk of developing TB based on demographic characteristics at time of landing.

METHODS

We included all individuals (n = 1 080 908) who became permanent residents of Canada between Jan. 1, 1985, and Dec. 31, 2012, and were resident in BC at any time between 1985 and 2013. Multiple administrative databases were linked to the provincial TB registry. We used recursive partitioning models to identify populations with high TB yield.

RESULTS

Active TB was diagnosed in 2814 individuals (incidence rate 24.2/100 000 person-years). Demographic factors (live-in caregiver, family, refugee immigration classes; higher TB incidence in country of birth; and older age) were strong predictors of TB incidence in BC, with elevated rates continuing many years after entry into the cohort. Recursive partitioning identified refugees 18-64 years of age from countries with a TB incidence greater than 224/100 000 population as a high-yield group, with 1% developing TB within the first 10 years.

INTERPRETATION

These findings support recommendations in Canadian guidelines to target postlanding screening for and treatment of LTBI in adult refugees from high-incidence countries. Because high-yield populations can be identified at entry via demographic data, screening at this point may be practical and high-impact, particularly if the LTBI care cascade can be optimized.

Tuberculosis among migrant workers in Taiwan

Background

Although the worldwide incidence of tuberculosis (TB) has been slowly decreasing, the migrant workers remains an important gap for regional TB control. In Taiwan, the numbers of the migrant workers from countries with high TB incidence increase significantly in past decades and the impact on public health remains unknown. This study aimed to explore the difference of TB incidence between Taiwanese and the migrant workers.

Methods

The migrant workers are obligated to receive pre-arrival, post-arrival and regular chest X-ray screening during their stay in Taiwan. We retrospectively collected these data extracted from the Alien Workers Health Database in Centers for Disease Control, Taiwan from Jan. 1, 2004 to Dec. 31, 2013. Poisson regression models were used to compare the hazard ratios of TB between Taiwanese and the migrant workers after adjusting gender and age groups.

Results

The total migrant workers in Taiwan reached 314,034 persons in 2004 and 489,134 persons in 2013, accounting for 2% of Taiwan population. The TB incidence of migrant workers was similar to Taiwanese (53–73.7 per 10⁵ vs 45.5–76.8 per 10⁵). Comparing with Taiwanese, the TB risk was significantly lower in male migrant workers (HR: 0.76; 95% CI: 0.70–0.83, P < 0.001), but higher in female migrant workers (HR: 1.40; 95% CI: 1.35–1.46, P < 0.001). Besides, we found that the TB risk in migrant workers was 5.30-fold (95% CI: 4.83–5.83, P < 0.001) in youngest group (≤24 year-old) comparing with Taiwanese.

Conclusions

Migrant workers in Taiwan have higher TB incidence than Taiwanese in young groups, especially in females. The mainstay young laborers with latent tuberculosis infection risk is an important vulnerability for public health. Further investigation and health screening are warranted.

Immigrant screening for latent tuberculosis infection: numbers needed to test and treat, a Norwegian population-based cohort study

OBJECTIVES

To estimate the number needed to screen (NNS) and the number needed to treat (NNT) to prevent one tuberculosis (TB) case in the Norwegian immigrant latent tuberculosis infection (LTBI) screening programme and to explore the effect of delay of LTBI treatment initiation.

DESIGN

Population-based, prospective cohort study.

PARTICIPANTS

Immigrants to Norway.

OUTCOME

Incident TB.

METHODS

We obtained aggregated data on immigration to Norway in 2008-2011 and used data from the Norwegian Surveillance System for Infectious Diseases to assess the number of TB cases arising in this cohort within 5 years after arrival. We calculated the average NNS and NNT for immigrants from the top 10 source countries for TB in Norway and by estimated TB incidence rates in source countries. We explored the sensitivity of these estimates with regard to test performance, treatment efficacy and treatment adherence using an extreme value approach, and assessed the effects of emigration, time to TB diagnosis (to define incident TB) and intervention timing.

RESULTS

NNS and NNT were overall high, with substantial variation. NNT showed numerically stronger negative correlation with TB notification rate in Norway (-0.75 [95% CI -1.00 to -0.44]) than with the WHO incidence rate (IR) (-0.32 [95% CI -0.93 to 0.29]). NNT was affected substantially by emigration and the definition of incident TB. Estimates were lowest for Somali (NNS 99 [70-150], NNT 27 [19-41]) and highest for Thai immigrants (NNS 585 [413-887], NNT 111 [79-116]). Implementing LTBI treatment in immigrants sooner after arrival may improve the effectiveness of the programme.

CONCLUSION

Using TB notifications in Norway, rather than IR in source countries, would improve targeting of immigrants for LTBI management. However, the overall high NNT is a concern and challenges the scale-up of preventive LTBI treatment for significant public health impact. Better data are urgently needed to monitor and evaluate NNS and NNT in countries implementing LTBI screening.

Latent tuberculosis infection: Opportunities and challenges

Diagnosing and treating latent tuberculosis (TB) infection (LTBI) is recognized by the World Health Organization as an important strategy to accelerate the decline in global TB and achieve TB elimination. Even among low-TB burden countries that have achieved high rates of detection and successful treatment for active TB, a number of barriers have prevented implementing or expanding LTBI treatment programmes. Of those infected with TB, relatively few will develop active disease and the current diagnostic tests have a low predictive value. LTBI treatment using isoniazid (INH) has low completion rates due to the long duration of therapy and poor tolerability. Both patients and physicians often perceive the risk of toxicity to be greater than the risk of reactivation TB. As a result, LTBI treatment has had a limited or negligible role outside of countries with high resources and low burden of disease. New tools have emerged including the interferon-gamma release assays that more accurately diagnose LTBI, particularly in people vaccinated with Bacillus Calmette-Guerin (BCG). Shorter, better tolerated treatment using rifamycins are proving safe and effective alternatives to INH. While still imperfect, TB prevention using these new diagnostic and treatment tools appear cost effective in modelling studies in the United States and have the potential to improve TB prevention efforts globally. Continued research to understand the host-organism interactions within the spectrum of LTBI is needed to develop better tools. Until then, overcoming the barriers and optimizing our current tools is essential for progressing toward TB elimination.

Predicting pulmonary tuberculosis in immigrants: a retrospective cohort study

Our objective was to investigate whether pulmonary tuberculosis (PTB) can be predicted from features of a targeted medical history and basic laboratory investigations in immigrants.

A retrospective cohort of 391 foreign-born adults referred to the Edmonton Tuberculosis Clinic (Edmonton, AB, Canada) was studied using multiple logistic regression analysis to predict PTB. Seven characteristics of disease were used as explanatory variables. Cross-validation assessed performance. Each predictor was tested on two outcomes: “culture-positive” and “smear-positive”. Receiver operating characteristic (ROC) curves were generated and the area under the ROC curve (AUC) was quantified.

Symptoms, subacute duration of symptoms, risk factors for reactivation of latent TB infection and anaemia were all associated with a positive culture (adjusted OR 1.79, 2.24, 1.72 and 2.28, respectively; p<0.05). Symptoms, inappropriate prescription of broad-spectrum antibiotics and a “typical” chest radiograph were associated with smear-positive PTB (adjusted OR 2.91, 1.55 and 12.34, respectively; p<0.05). ROC curve analysis was used to test each model, yielding AUC=0.91 for the outcome “culture-positive” disease and AUC=0.94 for the outcome “smear-positive” disease.

PTB among the foreign-born can be predicted from a targeted medical history and basic laboratory investigations, raising the threshold of suspicion in settings where the disease is relatively rare.

In high-income, low tuberculosis incidence countries, certain clinical characteristics should raise the threshold of suspicion to confirm a timely diagnosishttp://ow.ly/bRDZ30iPurz

Economic analysis of CDC's culture- and smear-based tuberculosis instructions for Filipino immigrants

SETTING

In 2007, the US Centers for Disease Control and Prevention (CDC) revised its tuberculosis (TB) technical instructions for panel physicians who administer mandatory medical examinations among US-bound immigrants. Many US-bound immigrants come from the Philippines, a high TB prevalence country.

OBJECTIVE

To quantify economic and health impacts of smear- vs. culture-based TB screening.

DESIGN

Decision tree modeling was used to compare three Filipino screening programs: 1) no screening, 2) smear-based screening, and 3) culture-based screening. The model incorporated pre-departure TB screening results from Filipino panel physicians and CDC databases with post-arrival follow-up outcomes. Costs (2013 $US) were examined from societal, immigrant, US Public Health Department and hospitalization perspectives.

RESULTS

With no screening, an annual cohort of 35 722 Filipino immigrants would include an estimated 450 TB patients with 264 hospitalizations, at a societal cost of US$9.90 million. Culture-based vs. smear-based screening would result in fewer imported cases (80.9 vs. 310.5), hospitalizations (19.7 vs. 68.1), and treatment costs (US$1.57 million vs. US$4.28 million). Societal screening costs, including US follow-up, were greater for culture-based screening (US$5.98 million) than for smear-based screening (US$3.38 million). Culture-based screening requirements increased immigrant costs by 61% (US$1.7 million), but reduced costs for the US Public Health Department (22%, US$750 000) and of hospitalization (70%, US$1 020 000).

CONCLUSION

Culture-based screening reduced imported TB and US costs among Filipino immigrants.

Spatial clusters of latent tuberculous infection, Connecticut, 2010-2014

SETTING

In the United States, tuberculosis (TB) control is increasingly focusing on the identification of persons with latent tuberculous infection (LTBI).

OBJECTIVE

To characterize the local epidemiology of LTBI in Connecticut, USA.

METHODS

We used spatial analyses 1) to identify census tract-level clusters of reported LTBI and TB disease in Connecticut, 2) to compare persons and populations in clusters with those not in clusters, and 3) to compare persons with LTBI to those with TB disease.

RESULTS

Significant census tract-level spatial clusters of LTBI and TB disease were identified. Compared with persons with LTBI in non-clustered census tracts, those in clustered census tracts were more likely to be foreign-born and less likely to be of white non-Hispanic ethnicity. Populations in census tract clusters of high LTBI prevalence had greater crowding, persons living in poverty, and persons lacking health care insurance than populations not in clustered census tracts. Persons with LTBI were less likely than those with TB disease to be of Asian ethnicity, and persons with LTBI were more likely than those with TB disease to reside in a clustered census tract.

CONCLUSIONS

Characterizing fine-scale populations at risk for LTBI supports effective and culturally accessible screening and treatment programs.

Cost-effectiveness of post-landing latent tuberculosis infection control strategies in new migrants to Canada

BACKGROUND

The majority of tuberculosis in migrants to Canada occurs due to reactivation of latent TB infection. Risk of tuberculosis in those with latent tuberculosis infection can be significantly reduced with treatment. Presently, only 2.4% of new migrants are flagged for post-landing surveillance, which may include latent tuberculosis infection screening; no other migrants receive routine latent tuberculosis infection screening. To aid in reducing the tuberculosis burden in new migrants to Canada, we determined the cost-effectiveness of using different latent tuberculosis infection interventions in migrants under post-arrival surveillance and in all new migrants.

METHODS

A discrete event simulation model was developed that focused on a Canadian permanent resident cohort after arrival in Canada, utilizing a ten-year time horizon, healthcare system perspective, and 1.5% discount rate. Latent tuberculosis infection interventions were evaluated in the population under surveillance (N = 6100) and the total cohort (N = 260,600). In all evaluations, six different screening and treatment combinations were compared to the base case of tuberculin skin test screening followed by isoniazid treatment only in the population under surveillance. Quality adjusted life years, incident tuberculosis cases, and costs were recorded for each intervention and incremental cost-effectiveness ratios were calculated in relation to the base case.

RESULTS

In the population under surveillance (N = 6100), using an interferon-gamma release assay followed by rifampin was dominant compared to the base case, preventing 4.90 cases of tuberculosis, a 4.9% reduction, adding 4.0 quality adjusted life years, and saving $353,013 over the ensuing ten-years. Latent tuberculosis infection screening in the total population (N = 260,600) was not cost-effective when compared to the base case, however could potentially prevent 21.8% of incident tuberculosis cases.

CONCLUSIONS

Screening new migrants under surveillance with an interferon-gamma release assay and treating with rifampin is cost saving, but will not significantly impact TB incidence. Universal latent tuberculosis infection screening and treatment is cost-prohibitive. Research into using risk factors to target screening post-landing may provide alternate solutions.

Comparing Drivers and Dynamics of Tuberculosis in California, Florida, New York, and Texas

RATIONALE

There is substantial state-to-state heterogeneity in tuberculosis (TB) in the United States; better understanding this heterogeneity can inform effective response to TB at the state level, the level at which most TB control efforts are coordinated.

OBJECTIVES

To characterize drivers of state-level heterogeneity in TB epidemiology in the four U.S. states that bear half the country's TB burden: California, Florida, New York, and Texas.

METHODS

We constructed an individual-based model of TB in the four U.S. states and calibrated the model to state-specific demographic and age- and nativity-stratified TB incidence data. We used the model to infer differences in natural history of TB and in future projections of TB.

MEASUREMENTS AND MAIN RESULTS

We found that differences in both demographic makeup (particularly the size and composition of the foreign-born population) and TB transmission dynamics contribute to state-level differences in TB epidemiology. The projected median annual rate of decline in TB incidence in the next decade was substantially higher in Texas (3.3%; 95% range, -5.6 to 10.9) than in California (1.7%; 95% range, -3.8 to 7.1), Florida (1.5%; 95% range, -7.4 to 14), and New York (1.9%; 95% range, -6.4 to 9.8). All scenarios projected a flattening of the decline in TB incidence by 2025 without additional resources or interventions.

CONCLUSIONS

There is substantial state-level heterogeneity in TB epidemiology in the four states, which reflect both demographic factors and potential differences in the natural history of TB. These differences may inform resource allocation decisions in these states.

Burden of non-adherence to latent tuberculosis infection drug therapy and the potential cost-effectiveness of adherence interventions in Canada: a simulation study

OBJECTIVE

Pharmaceutical treatment of latent tuberculosis infection (LTBI) reduces the risk of progression to active tuberculosis (TB); however, poor adherence tempers the protective effect. We aimed to estimate the health burden of non-adherence, the maximum allowable cost of hypothetical new adherence interventions to be cost-effective and the potential value of existing adherence interventions for patients with low-risk LTBI in Canada.

DESIGN

A microsimulation model of LTBI progression over 25 years.

SETTING

General practice in Canada.

PARTICIPANTS

Individuals with LTBI who are initiating drug therapy.

INTERVENTIONS

A hypothetical intervention with a range of effectiveness was evaluated. Existing drug adherence interventions including peer support, two-way text messaging support, enhanced adherence counselling and adherence incentives were also evaluated.

PRIMARY AND SECONDARY OUTCOME MEASURES

Simulation outcomes included healthcare costs, TB incidence, TB deaths and quality-adjusted life years (QALYs). Base case results were interpreted against a willingness-to-pay threshold of $C50 000/QALY.

RESULTS

Compared with current adherence levels, full adherence to LTBI drug therapy could reduce new TB cases from 90.3 cases per 100 000 person-years to 35.9 cases per 100 000 person-years and reduce TB-related deaths from 7.9 deaths per 100 000 person-years to 3.1 deaths per 100 000 person-years. An intervention that increases relative adherence by 40% would bring the population near full adherence to drug therapy and could have a maximum allowable annual cost of approximately $C450 per person to be cost-effective. Based on estimates of effect sizes and costs of existing adherence interventions, we found that they yielded between 900 and 2400 additional QALYs per million people, reduced TB deaths by 5%-25% and were likely to be cost-effective over 25 years.

CONCLUSION

Full adherence could reduce the number of future TB cases by nearly 60%, offsetting TB-related costs and health burden. Several existing interventions are could be cost-effective to help achieve this goal.

Post-migration follow-up of migrants identified to be at increased risk of developing tuberculosis at pre-migration screening: a systematic review and meta-analysis

BACKGROUND

Post-migration follow-up of migrants considered at increased risk of developing tuberculosis based on pre-migration screening abnormalities (high-risk migrants) is implemented in several low-incidence countries. We aimed to determine the rate of tuberculosis in this population to inform cross-border tuberculosis control policies.

METHODS

We searched MEDLINE and Embase (since inception to Jan 12, 2017) for studies evaluating post-migration follow-up of high-risk migrants. Outcomes evaluated were the number of tuberculosis cases occurring post-migration, expressed as the tuberculosis incidence per 100 000 person-years of follow-up, as cumulative incidence of tuberculosis per 100 000 persons, and the cumulative incidence of tuberculosis at the first post-migration follow-up visit. Random-effects models were used to summarise outcomes across studies.

FINDINGS

We identified 20 publications (describing 23 study cohorts) reporting the pre-migration screening outcomes of 8 355 030 migrants processed between Jan 1, 1981, and May 1, 2014, with 222 375 high-risk migrants identified. The pooled cumulative incidence of tuberculosis post-migration in our study population from 22 cohorts was 2794 per 100 000 persons (95% CI 2179-3409; I2=99%). The pooled cumulative incidence of tuberculosis at the first follow-up visit from ten cohorts was 3284 per 100 000 persons (95% CI 2173-4395; I2=99%). The pooled tuberculosis incidence from 15 cohorts was 1249 per 100 000 person-years of follow-up (95% CI 924-1574; I2=98%).

INTERPRETATION

The high rate of tuberculosis in high-risk migrants suggests that tuberculosis control measures in this population, including more sensitive pre-migration screening, preventive treatment of latent tuberculosis infection, or post-migration follow-up, are potentially effective cross-border tuberculosis control strategies in low-incidence countries.

FUNDING

Australian National Health and Medical Research Council.

Use of Transnational Services to Prevent Treatment Interruption in Tuberculosis-Infected Persons Who Leave the United States

Scale up of such services is possible and encouraged because of potential health gains and reduced healthcare costs.

A major problem resulting from interrupted tuberculosis (TB) treatment is the development of drug-resistant TB, including multidrug-resistant TB (MDR TB), a more deadly and costly-to-treat form of the disease. Global health systems are not equipped to diagnose and treat the current burden of MDR TB. TB-infected foreign visitors and temporary US residents who leave the country during treatment can experience treatment interruption and, thus, are at greater risk for drug-resistant TB. Using epidemiologic and demographic data, we estimated TB incidence among this group, as well as the proportion of patients referred to transnational care–continuity and management services during relocation; each year, ≈2,827 visitors and temporary residents are at risk for TB treatment interruption, 222 (8%) of whom are referred for transnational services. Scale up of transnational services for persons at high risk for treatment interruption is possible and encouraged because of potential health gains and reductions in healthcare costs for the United States and receiving countries.

Tuberculosis progression rates in U.S. Immigrants following screening with interferon-gamma release assays

Background

Interferon-gamma release assays may be used as an alternative to the tuberculin skin test for detection of M. tuberculosis infection. However, the risk of active tuberculosis disease following screening using interferon-gamma release assays in immigrants is not well defined. To address these uncertainties, we determined the incidence rates of active tuberculosis disease in a cohort of high-risk immigrants with Class B TB screened with interferon-gamma release assays (IGRAs) upon arrival in the United States.

Methods

Using a retrospective cohort design, we enrolled recent U.S. immigrants with Class B TB who were screened with an IGRA (QuantiFERON ® Gold or Gold In-Tube Assay) at the San Francisco Department of Public Health Tuberculosis Control Clinic from January 2005 through December 2010. We reviewed records from the Tuberculosis Control Patient Management Database and from the California Department of Public Health Tuberculosis Case Registry to determine incident cases of active tuberculosis disease through February 2015.

Results

Of 1233 eligible immigrants with IGRA screening at baseline, 81 (6.6 %) were diagnosed with active tuberculosis disease as a result of their initial evaluation. Of the remaining 1152 participants without active tuberculosis disease at baseline, 513 tested IGRA-positive and 639 tested IGRA-negative. Seven participants developed incident active tuberculosis disease over 7730 person-years of follow-up, for an incidence rate of 91 per 100,000 person-years (95 % CI 43–190). Five IGRA-positive and two IGRA-negative participants developed active tuberculosis disease (incidence rates 139 per 100,000 person-years (95 % CI 58–335) and 48 per 100,000 person-years (95 % CI 12–193), respectively) for an unadjusted incidence rate ratio of 2.9 (95 % CI 0.5–30, p = 0.21). IGRA test results had a negative predictive value of 99.7 % but a positive predictive value of only 0.97 %.

Conclusions

Among high-risk immigrants without active tuberculosis disease at the time of entry into the United States, risk of progression to active tuberculosis disease was higher in IGRA-positive participants compared with IGRA-negative participants. However, these findings did not reach statistical significance, and a positive IGRA at enrollment had a poor predictive value for progressing to active tuberculosis disease. Additional research is needed to identify biomarkers and develop clinical algorithms that can better predict progression to active tuberculosis disease among U.S. immigrants.

Mycobacterium Tuberculosis Infection, Immigration Status, and Diagnostic Discordance: A Comparison of Tuberculin Skin Test and QuantiFERON-TB Gold In-Tube Test Among Immigrants to the U.S

OBJECTIVE

We used a recent source of nationally representative population data on tuberculosis (TB) infection to characterize concordance between the tuberculin skin test (TST) and the QuantiFERON-TB Gold In-Tube (QFT-GIT) blood test for immigrants in the United States.

METHODS

We used TB screening data from the 2011-2012 National Health and Nutrition Examination Survey to examine concordance between the TST and QFT-GIT--an interferon-gamma release assay (IGRA) blood test--for 7,097 U.S. natives, naturalized citizens, and noncitizens.

RESULTS

Consistent with prior findings, one in five immigrants in the survey was identified with latent TB infection (LTBI), a rate 14 times higher than for U.S. natives. We also found higher rates of discordant TST/IGRA results among immigrants than among U.S. natives. Unadjusted discordance between TST and IGRA was 3% among U.S. natives (weighted N=5,684,274 of 191,179,213) but ranged up to 19% for noncitizens (weighted N=3,722,960 of 19,377,147). Adjusting for age, sex, and race/ethnicity, noncitizens had more than nine times the odds of having a positive TST result but negative QFT-GIT result compared with U.S. natives.

CONCLUSIONS

Our findings suggest that whether and how either of these tests should be deployed is highly context sensitive. Significant discordance in test results when used among immigrants raises the possibility of missed opportunities for harm reduction in this already at-risk population. However, we found little distinction between the tests in terms of diagnostic outcome when used in a U.S. native population, suggesting little benefit to the adoption and use of the QFT-GIT test in place of TST on the basis of test performance alone for this population.

Getting to Zero: Tuberculosis Elimination in California

This review of tuberculosis epidemiology is intended to provide a historical perspective on the public health approach to tuberculosis (TB) control in California. This historical context offers a lens through which to view current epidemiologic trends and insight into how new therapeutic tools can be applied. Since 1993, the year detailed case reporting was instituted, California has had a decrease in recent TB transmission as evidenced by a reduction in pediatric cases and an increased percentage of cases attributable to progression of latent infection to TB disease in the foreign-born population. Overall, there has been a dramatic decline in the annual TB case count, but the speed of the decline has slowed over the last several years. At the current pace and case count of 2137 in 2015, California will not achieve TB elimination (<1 TB case per one million population) for at least 100 years. There are an estimated 2.1 million persons in California with latent TB infection. Modeling suggests that LTBI detection and treatment are important in reaching TB elimination. For this reason, a coalition of stakeholders in California is exploring novel approaches to accelerate the case decline in order to prevent unnecessary disease and death.

Mind the gap: TB trends in the USA and the UK, 2000-2011

BACKGROUND

TB remains a major public health concern, even in low-incidence countries like the USA and the UK. Over the last two decades, cases of TB reported in the USA have declined, while they have increased substantially in the UK. We examined factors associated with this divergence in TB trends between the two countries.

METHODS

We analysed all cases of TB reported to the US and UK national TB surveillance systems from 1 January 2000 through 31 December 2011. Negative binominal regression was used to assess potential demographic, clinical and risk factor variables associated with differences in observed trends.

FINDINGS

A total of 259,609 cases were reported. From 2000 to 2011, annual TB incidence rates declined from 5.8 to 3.4 cases per 100,000 in the USA, whereas in the UK, TB incidence increased from 11.4 to 14.4 cases per 100,000. The majority of cases in both the USA (56%) and the UK (64%) were among foreign-born persons. The number of foreign-born cases reported in the USA declined by 15% (7731 in 2000 to 6564 in 2011) while native-born cases fell by 54% (8442 in 2000 to 3883 in 2011). In contrast, the number of foreign-born cases reported in the UK increased by 80% (3380 in 2000 to 6088 in 2011), while the number of native-born cases remained largely unchanged (2158 in 2000 to 2137 in 2011). In an adjusted negative binomial regression model, significant differences in trend were associated with sex, age, race/ethnicity, site of disease, HIV status and previous history of TB (p<0.01). Among the foreign-born, significant differences in trend were also associated with time since UK or US entry (p<0.01).

INTERPRETATION

To achieve TB elimination in the UK, a re-evaluation of current TB control policies and practices with a focus on foreign-born are needed. In the USA, maintaining and strengthening control practices are necessary to sustain the progress made over the last 20 years.

Abrupt Decline in Tuberculosis among Foreign-Born Persons in the United States

While the number of reported tuberculosis (TB) cases in the United States has declined over the past two decades, TB morbidity among foreign-born persons has remained persistently elevated. A recent unexpected decline in reported TB cases among foreign-born persons beginning in 2007 provided an opportunity to examine contributing factors and inform future TB control strategies. We investigated the relative influence of three factors on the decline: 1) changes in the size of the foreign-born population through immigration and emigration, 2) changes in distribution of country of origin among foreign-born persons, and 3) changes in the TB case rates among foreign-born subpopulations. Using data from the U.S. National Tuberculosis Surveillance System and the American Community Survey, we examined TB case counts, TB case rates, and population estimates, stratified by years since U.S. entry and country of origin. Regression modeling was used to assess statistically significant changes in trend. Among foreign-born recent entrants (<3 years since U.S. entry), we found a 39.5% decline (-1,013 cases) beginning in 2007 (P<0.05 compared to 2000–2007) and ending in 2011 (P<0.05 compared to 2011–2014). Among recent entrants from Mexico, 80.7% of the decline was attributable to a decrease in population, while the declines among recent entrants from the Philippines, India, Vietnam, and China were almost exclusively (95.5%–100%) the result of decreases in TB case rates. Among foreign-born non-recent entrants (≥3 years since U.S. entry), we found an 8.9% decline (-443 cases) that resulted entirely (100%) from a decrease in the TB case rate. Both recent and non-recent entrants contributed to the decline in TB cases; factors contributing to the decline among recent entrants varied by country of origin. Strategies that impact both recent and non-recent entrants (e.g., investment in overseas TB control) as well as those that focus on non-recent entrants (e.g., expanded targeted testing of high-risk subgroups among non-recent entrants) will be necessary to achieve further declines in TB morbidity among foreign-born persons.

Transnational Record Linkage for Tuberculosis Surveillance and Program Evaluation

OBJECTIVE

Pre-immigration tuberculosis (TB) screening, followed by post-arrival rescreening during the first year, is critical to reducing TB among foreign-born people in the United States. However, existing U.S. public health surveillance is inadequate to monitor TB among immigrants during subsequent years. We developed and tested a novel method for ascertaining post-U.S.-arrival TB outcomes among high-TB-risk immigrant cohorts to improve surveillance.

METHODS

We used a probabilistic record linkage program to link pre-immigration screening records from U.S.-bound immigrants from the Philippines (n=422,593) and Vietnam (n=214,401) with the California TB registry during 2000-2010. We estimated sensitivity using Monte Carlo simulations to account for uncertainty in key inputs. Specificity was evaluated by using a time-stratified approach, which defined false-positives as TB records linked to pre-immigration screening records dated after the person had arrived in the United States.

RESULTS

TB was reported in 4,382 and 2,830 people born in the Philippines and Vietnam, respectively, in California during the study period. Of these TB cases, records for 973 and 452 cases of people born in the Philippines and Vietnam, respectively, were linked to pre-immigration screening records. Sensitivity and specificity of linkage were 89% (90% credible interval [CrI] 83, 97) and 100%, respectively, for the Philippines, and 90% (90% CrI 83, 98) and 99.9%, respectively, for Vietnam.

CONCLUSION

Electronic linkage of pre-immigration screening records to a domestic TB registry was feasible, sensitive, and highly specific in two high-priority immigrant cohorts. Transnational record linkage can be used for program evaluation and routine monitoring of post-U.S.-arrival TB risk among immigrants, but requires interagency data sharing and collaboration.

A cost-benefit analysis of a proposed overseas refugee latent tuberculosis infection screening and treatment program

BACKGROUND

This study explored the effect of screening and treatment of refugees for latent tuberculosis infection (LTBI) before entrance to the United States as a strategy for reducing active tuberculosis (TB). The purpose of this study was to estimate the costs and benefits of LTBI screening and treatment in United States bound refugees prior to arrival.

METHODS

Costs were included for foreign and domestic LTBI screening and treatment and the domestic treatment of active TB. A decision tree with multiple Markov nodes was developed to determine the total costs and number of active TB cases that occurred in refugee populations that tested 55, 35, and 20 % tuberculin skin test positive under two models: no overseas LTBI screening and overseas LTBI screening and treatment. For this analysis, refugees that tested 55, 35, and 20 % tuberculin skin test positive were divided into high, moderate, and low LTBI prevalence categories to denote their prevalence of LTBI relative to other refugee populations.

RESULTS

For a hypothetical 1-year cohort of 100,000 refugees arriving in the United States from regions with high, moderate, and low LTBI prevalence, implementation of overseas screening would be expected to prevent 440, 220, and 57 active TB cases in the United States during the first 20 years after arrival. The cost savings associated with treatment of these averted cases would offset the cost of LTBI screening and treatment for refugees from countries with high (net cost-saving: $4.9 million) and moderate (net cost-saving: $1.6 million) LTBI prevalence. For low LTBI prevalence populations, LTBI screening and treatment exceed expected future TB treatment cost savings (net cost of $780,000).

CONCLUSIONS

Implementing LTBI screening and treatment for United States bound refugees from countries with high or moderate LTBI prevalence would potentially save millions of dollars and contribute to United States TB elimination goals. These estimates are conservative since secondary transmission from tuberculosis cases in the United States was not considered in the model.

A systematic review on TST and IGRA tests used for diagnosis of LTBI in immigrants

BACKGROUND

High immigration rates from tuberculosis (TB) endemic countries to low-incidence countries have caused new TB guidelines in these countries to reconsider latent TB infection (LTBI) screening in these immigrants.

OBJECTIVES

We performed a systematic review with the primary outcome of evaluating the number of cases recommended LTBI treatment with the tuberculin skin test (TST) or interferon gamma release assay (IGRA). Secondary objectives were to examine prevalence of positive LTBI diagnostic tests stratified by age and incidence of TB in country of origin.

METHODS

We performed a systematic search of seven electronic databases for studies assessing TST and/or IGRA performance in immigrant populations to low incidence countries. Demographics, LTBI diagnosis, longitudinal TB development, and test result data were the primary data extracted from the studies. Prevalence of positive test data was stratified by age and country of origin. Studies were evaluated using a modified SIGN checklist for diagnostic studies. Data was compared using Fisher's exact test or χ (2) test, where appropriate.

RESULTS

Our literature search yielded 51 studies (n = 34 TST, n = 9 IGRA, n = 8 both). Recommendation of LTBI treatment was less common in those tested with an IGRA compared to TST (p < 0.0001), while long-term development of active TB appears higher in those with a positive IGRA. There was no difference in the sensitivity and specificity of the IGRA and TST for prevalent TB (p > 0.05). Prevalence of a positive test was significantly lower in those who were <18 years of age compared to those ≥18 years of age (p < 0.0001) and those from low TB incidence countries compared to high incidence countries (p < 0.0001) for both TST and IGRA. When comparing the two tests within the 2 subgroups: age and TB incidence in country of origin, the prevalence of positive results was significantly lower for the IGRA than the TST (p < 0.0001).

LIMITATIONS

The number of available studies evaluating the IGRA and longitudinal active TB development in those tested limits this study.

CONCLUSION

Prevalence of positive test results were significantly lower in immigrants who were tested with an IGRA, resulting in fewer immigrants being recommended for LTBI treatment compared to TST. Coupled with comparable performance for detecting prevalent TB cases, the IGRA appears to exhibit better specificity than the TST and may be preferred as the standard of care for detecting LTBI in immigrants moving to low TB incidence countries.

Permutations of time and place in tuberculosis

Tuberculosis remains a global health pandemic. The current depiction of the Mycobacterium tuberculosis life cycle proposes that airborne bacilli are inhaled and phagocytosed by alveolar macrophages, resulting in the formation of a granuloma that ruptures into the airways to reinitiate the infectious cycle. However, this widely proposed model overlooks the fact, established 100 years ago, that the initial site of M tuberculosis implantation is in the lower zones of the lungs, whereas infectious cavitary pulmonary disease develops at the lung apices. The immunological events at these two pulmonary locations are different--cavitation only occurs in the apices and not in the bases. Yet the current conceptual model of tuberculosis renders the immunology of these two temporally and spatially separated events identical. One key consequence is that prevention of primary childhood tuberculosis at the lung bases is regarded as adequate immunological protection, but extensive evidence shows that greater immunity could predispose to immunopathology and transmission at the lung apex. A much greater understanding of time and place in the immunopathological mechanisms underlying human tuberculosis is needed before further pre-exposure vaccination trials can be done.

Preventing Infectious Pulmonary Tuberculosis Among Foreign-Born Residents of the United States

OBJECTIVES

We described risk factors associated with infectious tuberculosis (TB) and missed TB-prevention opportunities in foreign-born US residents, who account for almost two thirds of the nation's TB patients.

METHODS

In a cross-sectional study at 20 US sites of foreign-born persons diagnosed with TB in 2005 through 2006, we collected results of sputum smear microscopy for acid-fast bacilli (a marker for infectiousness) and data on visa status, sociodemographics, TB-related care seeking, and latent TB infection (LTBI) diagnosis opportunities.

RESULTS

Among 980 persons with pulmonary TB who reported their visa status, 601 (61%) were legal permanent residents, 131 (13.4%) had temporary visas, and 248 (25.3%) were undocumented. Undocumented persons were more likely than permanent residents to have acid-fast bacilli-positive smears at diagnosis (risk ratio = 1.3; 95% confidence interval = 1.2, 1.4). Of those diagnosed 1 year or more after arrival, 57.3% reported LTBI screening opportunities; fewer than 25% actually were. Undocumented persons reported fewer LTBI screening opportunities and were less likely to be tested.

CONCLUSIONS

Progress toward TB elimination in the United States depends upon expanding opportunities for regular medical care and promotion of LTBI screening and treatment among foreign-born persons.

The TB-specific CD4(+) T cell immune repertoire in both cynomolgus and rhesus macaques largely overlap with humans

Non-human primate (NHP) models of tuberculosis (TB) immunity and pathogenesis, especially rhesus and cynomolgus macaques, are particularly attractive because of the high similarity of the human and macaque immune systems. However, little is known about the MHC class II epitopes recognized in macaques, thus hindering the establishment of immune correlates of immunopathology and protective vaccination. We characterized immune responses in rhesus macaques vaccinated against and/or infected with Mycobacterium tuberculosis (Mtb), to a panel of antigens currently in human vaccine trials. We defined 54 new immunodominant CD4(+) T cell epitopes, and noted that antigens immunodominant in humans are also immunodominant in rhesus macaques, including Rv3875 (ESAT-6) and Rv3874 (CFP10). Pedigree and inferred restriction analysis demonstrated that this phenomenon was not due to common ancestry or inbreeding, but rather presentation by common alleles, as well as, promiscuous binding. Experiments using a second cohort of rhesus macaques demonstrated that a pool of epitopes defined in the previous experiments can be used to detect T cell responses in over 75% of individual monkeys. Additionally, 100% of cynomolgus macaques, irrespective of their latent or active TB status, responded to rhesus and human defined epitope pools. Thus, these findings reveal an unexpected general repertoire overlap between MHC class II epitopes recognized in both species of macaques and in humans, showing that epitope pools defined in humans can also be used to characterize macaque responses, despite differences in species and antigen exposure. The results have general implications for the evaluation of new vaccines and diagnostics in NHPs, and immediate applicability in the setting of macaque models of TB.

Maintaining sharp focus on a grainy film: miliary pattern in an elderly woman with acute respiratory failure

An elderly woman with a history of pulmonary tuberculosis reportedly diagnosed and treated 30 years prior to presentation was found unresponsive at home. Chest imaging revealed innumerable pulmonary nodules worrisome for an infectious process, specifically tuberculosis. The patient deteriorated rapidly and in accordance with her wishes, aggressive interventions were withheld. She died within 48 h from respiratory failure. A limited chest autopsy was performed and revealed the cause of death as lymphangitic spread of cancer from a primary lung adenocarcinoma.

Civil Surgeon Tuberculosis Evaluations for Foreign-Born Persons Seeking Permanent U.S. Residence

Foreign-born persons in the United States seeking to adjust their status to permanent resident must undergo screening for tuberculosis (TB) disease. Screening is performed by civil surgeons (CS) following technical instructions by the Centers for Disease Control and Prevention. From 2011 to 2012, 1,369 practicing CS in California, Texas, and New England were surveyed to investigate adherence to the instructions. A descriptive analysis was conducted on 907 (66%) respondents. Of 907 respondents, 739 (83%) had read the instructions and 565 (63%) understood that a chest radiograph is required for status adjustors with TB symptoms; however, only 326 (36%) knew that a chest radiograph is required for immunosuppressed status adjustors. When suspecting TB disease, 105 (12%) would neither report nor refer status adjustors to the health department; 91 (10%) would neither start treatment nor refer for TB infection. Most CS followed aspects of the technical instructions; however, educational opportunities are warranted to ensure positive patient outcomes.

Decline in tuberculosis among Mexico-born persons in the United States, 2000-2010

BACKGROUND

In 2010, Mexico was the most common (22.9%) country of origin for foreign-born persons with tuberculosis in the United States, and overall trends in tuberculosis morbidity are substantially influenced by the Mexico-born population.

OBJECTIVES

To determine the risk of tuberculosis disease among Mexico-born persons living in the United States.

METHODS

Using data from the U.S. National Tuberculosis Surveillance System and the American Community Survey, we examined tuberculosis case counts and case rates stratified by years since entry into the United States and geographic proximity to the United States-Mexico border. We calculated trends in case rates over time measured by average annual percent change.

RESULTS

The total tuberculosis case count (-14.5%) and annual tuberculosis case rate (average annual percent change -5.1%) declined among Mexico-born persons. Among those diagnosed with tuberculosis less than 1 year since entry into the United States (newly arrived persons), there was a decrease in tuberculosis cases (-60.4%), no change in tuberculosis case rate (average annual percent change of 0.0%), and a decrease in population (-60.7%). Among those living in the United States for more than 5 years (non-recently arrived persons), there was an increase in tuberculosis cases (+3.4%), a decrease in tuberculosis case rate (average annual percent change of -4.9%), and an increase in population (+62.7%). In 2010, 66.7% of Mexico-born cases were among non-recently arrived persons, compared with 51.1% in 2000. Although border states reported the highest proportions (>15%) of tuberculosis cases that were Mexico-born, the highest Mexico-born-specific tuberculosis case rates (>20/100,000 population) were in states in the eastern and southeastern regions of the United States.

CONCLUSIONS

The decline in tuberculosis morbidity among Mexico-born persons may be attributed to fewer newly arrived persons from Mexico and lower tuberculosis case rates among non-recently arrived Mexico-born persons. The extent of the decline was dampened by an unchanged tuberculosis case rate among newly arrived persons from Mexico and a large increase in the non-recently arrived Mexico-born population. If current trends continue, tuberculosis morbidity among Mexico-born persons will be increasingly driven by those who have been living in the United States for more than 5 years.