Economic analysis of different throughput scenarios and implementation strategies of computer-aided detection software as a screening and triage test for pulmonary TB.

BACKGROUND: Artificial Intelligence (AI) systems have demonstrated potential in detecting tuberculosis (TB) associated abnormalities from chest X-ray (CXR) images. Thus, they might provide a solution to radiologist shortages in high TB burden countries. However, the cost of implementing computer-aided detection (CAD) software has thus far been understudied. In this study, we performed a costing analysis of CAD software when used as a screening or triage test for pulmonary TB, estimated the incremental cost compared to a radiologist reading of different throughput scenarios, and predicted the cost for the national scale-up plan in Pakistan. METHODS: For the study, we focused on CAD software reviewed by the World Health Organization (CAD4TB, Lunit INSIGHT CXR, qXR) or listed in the Global Drug Facility diagnostics catalogue (CAD4TB, InferRead). Costing information was obtained from the CAD software developers. CAD4TB and InferRead use a perpetual license pricing model, while Lunit and qXR are priced per license for restricted number of scans. A major implementer in Pakistan provided costing information for human resource and software training. The per-screen cost was estimated for each CAD software and for radiologist for 1) active case finding, and 2) facility based CXR testing scenarios with throughputs ranging from 50,000-100,000 scans. Moreover, we estimated the scale-up cost for CAD or radiologist CXR reading in Pakistan based on the National Strategic Plan, considering that to reach 80% diagnostic coverage, 50% of TB patients would need to be found through facility-based triage and 30% through active case finding (ACF). RESULTS: The per-screen cost for CAD4TB (0.25 USD- 2.33 USD) and InferRead (0.19 USD- 2.78 USD) was lower than that of a radiologist (0.70 USD- 0.93 USD) for high throughput scenarios studied. In comparison, the per-screen cost for Lunit (0.94 USD- 1.69 USD) and qXR (0.95 USD-1.9 USD) were only comparable with that of the radiologists in the highest throughput scenario in ACF. To achieve 80 percent diagnostic coverage at scale in Pakistan, the projected additional cost of deploying CAD software to complement the current infrastructure over a four-year period were estimated at 2.65-19.23 million USD, whereas Human readers, would cost an additional 23.97 million USD. CONCLUSIONS: Our findings suggest that using CAD software could enable large-scale screening programs in high TB-burden countries and be less costly than radiologist. To achieve minimum cost, the target number of screens in a specific screening strategy should be carefully considered when selecting CAD software, along with the offered pricing structure and other aspects such as performance and operational features. Integrating CAD software in implementation strategies for case finding could be an economical way to attain the intended programmatic goals.

Intelligent tuberculosis activity assessment system based on an ensemble of neural networks.

This article proposes a novel approach to assess the degree of activity of pulmonary tuberculosis by active tuberculoma foci. It includes the development of a new method for processing lung CT images using an ensemble of deep convolutional neural networks using such special algorithms: an optimized algorithm for preliminary segmentation and selection of informative scans, a new algorithm for refining segmented masks to improve the final accuracy, an efficient fuzzy inference system for more weighted activity assessment. The approach also includes the use of medical classification of disease activity based on densitometric measures of tuberculomas. The selection and markup of the training sample images were performed manually by qualified pulmonologists from a base of approximately 9,000 CT lung scans of patients who had been enrolled in the dispensary for 15 years. The first basic step of the proposed approach is the developed algorithm for preprocessing CT lung scans. It consists in segmentation of intrapulmonary regions, which contain vessels, bronchi, lung walls to detect complex cases of ingrown tuberculomas. To minimize computational cost, the proposed approach includes a new method for selecting informative lung scans, i.e., those that potentially contain tuberculomas. The main processing step is binary segmentation of tuberculomas, which is proposed to be performed optimally by a certain ensemble of neural networks. Optimization of the ensemble size and its composition is achieved by using an algorithm for calculating individual contributions. A modification of this algorithm using new effective heuristic metrics has been proposed which improves the performance of the algorithm for this problem. A special algorithm was developed for post-processing of tuberculoma masks obtained during the segmentation step. The goal of this step is to refine the calculated mask for the physical placement of the tuberculoma. The algorithm consists in cleaning the mask from noisy formations on the scan, as well as expanding the mask area to maximize the capture of the tuberculoma location area. A simplified fuzzy inference system was developed to provide a more accurate final calculation of the degree of disease activity, which reflects data from current medical studies. The accuracy of the system was also tested on a test sample of independent patients, showing more than 96% correct calculations of disease activity, confirming the effectiveness and feasibility of introducing the system into clinical practice.

Symptom- and chest-radiography screening for active pulmonary tuberculosis in HIV-negative adults and adults with unknown HIV status.

BACKGROUND: Systematic screening in high-burden settings is recommended as a strategy for early detection of pulmonary tuberculosis disease, reducing mortality, morbidity and transmission, and improving equity in access to care. Questioning for symptoms and chest radiography (CXR) have historically been the most widely available tools to screen for tuberculosis disease. Their accuracy is important for the design of tuberculosis screening programmes and determines, in combination with the accuracy of confirmatory diagnostic tests, the yield of a screening programme and the burden on individuals and the health service. OBJECTIVES: To assess the sensitivity and specificity of questioning for the presence of one or more tuberculosis symptoms or symptom combinations, CXR, and combinations of these as screening tools for detecting bacteriologically confirmed pulmonary tuberculosis disease in HIV-negative adults and adults with unknown HIV status who are considered eligible for systematic screening for tuberculosis disease. Second, to investigate sources of heterogeneity, especially in relation to regional, epidemiological, and demographic characteristics of the study populations. SEARCH METHODS: We searched the MEDLINE, Embase, LILACS, and HTA (Health Technology Assessment) databases using pre-specified search terms and consulted experts for unpublished reports, for the period 1992 to 2018. The search date was 10 December 2018. This search was repeated on 2 July 2021. SELECTION CRITERIA: Studies were eligible if participants were screened for tuberculosis disease using symptom questions, or abnormalities on CXR, or both, and were offered confirmatory testing with a reference standard. We included studies if diagnostic two-by-two tables could be generated for one or more index tests, even if not all participants were subjected to a microbacteriological reference standard. We excluded studies evaluating self-reporting of symptoms. DATA COLLECTION AND ANALYSIS: We categorized symptom and CXR index tests according to commonly used definitions. We assessed the methodological quality of included studies using the QUADAS-2 instrument. We examined the forest plots and receiver operating characteristic plots visually for heterogeneity. We estimated summary sensitivities and specificities (and 95% confidence intervals (CI)) for each index test using bivariate random-effects methods. We analyzed potential sources of heterogeneity in a hierarchical mixed-model. MAIN RESULTS: The electronic database search identified 9473 titles and abstracts. Through expert consultation, we identified 31 reports on national tuberculosis prevalence surveys as eligible (of which eight were already captured in the search of the electronic databases), and we identified 957 potentially relevant articles through reference checking. After removal of duplicates, we assessed 10,415 titles and abstracts, of which we identified 430 (4%) for full text review, whereafter we excluded 364 articles. In total, 66 articles provided data on 59 studies. We assessed the 2 July 2021 search results; seven studies were potentially eligible but would make no material difference to the review findings or grading of the evidence, and were not added in this edition of the review. We judged most studies at high risk of bias in one or more domains, most commonly because of incorporation bias and verification bias. We judged applicability concerns low in more than 80% of studies in all three domains. The three most common symptom index tests, cough for two or more weeks (41 studies), any cough (21 studies), and any tuberculosis symptom (29 studies), showed a summary sensitivity of 42.1% (95% CI 36.6% to 47.7%), 51.3% (95% CI 42.8% to 59.7%), and 70.6% (95% CI 61.7% to 78.2%, all very low-certainty evidence), and a specificity of 94.4% (95% CI 92.6% to 95.8%, high-certainty evidence), 87.6% (95% CI 81.6% to 91.8%, low-certainty evidence), and 65.1% (95% CI 53.3% to 75.4%, low-certainty evidence), respectively. The data on symptom index tests were more heterogenous than those for CXR. The studies on any tuberculosis symptom were the most heterogeneous, but had the lowest number of variables explaining this variation. Symptom index tests also showed regional variation. The summary sensitivity of any CXR abnormality (23 studies) was 94.7% (95% CI 92.2% to 96.4%, very low-certainty evidence) and 84.8% (95% CI 76.7% to 90.4%, low-certainty evidence) for CXR abnormalities suggestive of tuberculosis (19 studies), and specificity was 89.1% (95% CI 85.6% to 91.8%, low-certainty evidence) and 95.6% (95% CI 92.6% to 97.4%, high-certainty evidence), respectively. Sensitivity was more heterogenous than specificity, and could be explained by regional variation. The addition of cough for two or more weeks, whether to any (pulmonary) CXR abnormality or to CXR abnormalities suggestive of tuberculosis, resulted in a summary sensitivity and specificity of 99.2% (95% CI 96.8% to 99.8%) and 84.9% (95% CI 81.2% to 88.1%) (15 studies; certainty of evidence not assessed). AUTHORS' CONCLUSIONS: The summary estimates of the symptom and CXR index tests may inform the choice of screening and diagnostic algorithms in any given setting or country where screening for tuberculosis is being implemented. The high sensitivity of CXR index tests, with or without symptom questions in parallel, suggests a high yield of persons with tuberculosis disease. However, additional considerations will determine the design of screening and diagnostic algorithms, such as the availability and accessibility of CXR facilities or the resources to fund them, and the need for more or fewer diagnostic tests to confirm the diagnosis (depending on screening test specificity), which also has resource implications. These review findings should be interpreted with caution due to methodological limitations in the included studies and regional variation in sensitivity and specificity. The sensitivity and specificity of an index test in a specific setting cannot be predicted with great precision due to heterogeneity. This should be borne in mind when planning for and implementing tuberculosis screening programmes.

Assessment of Post-Treatment Health-Related Quality of Life among Patients with Pulmonary Tuberculosis in Ilorin, Nigeria.

BACKGROUND: A lot of attention has generally been given to the microbiology and treatment of pulmonary tuberculosis with relatively limited consideration on its impact on the physical, psychological and social domains of the individual especially after successful drug treatment. AIM AND OBJECTIVES: This study aimed at assessing the health-related quality of life (HRQoL) and related factors among individuals who had successfully completed treatment for pulmonary tuberculosis (PTB) in Ilorin. METHODS: This was a hospital based cross-sectional study at the pulmonary outpatient clinics of the University of Ilorin Teaching Hospital and Kwara State Specialist Hospital, Sobi, Ilorin. HRQoL assessment was conducted in 308 consenting patients who had been certified microbiologically cured for bacteriologically confirmed PTB in the preceding three years using the validated St. George's Respiratory Questionnaire (SGRQ). All subjects also had plain chest radiograph done for assessment of the presence and extent of lung parenchymal damage. RESULTS: The overall total median percentage HRQoL score was 18.5 (7.9-28.2) with the highest score in the activity component [33.7 (18.3-41.8)] and least scores in the impact component [10.0 (0.0-21.9)]. The independent predictors of impaired HRQoL were age > 40 years (p= 0.007), absence of formal education (p=0.004), mMRC score >1 (p= 0.002), PTB retreatment (p=<0.001) and radiographic scores >3 (p= <0.001). CONCLUSION: There is impaired HRQoL following treatment for PTB in Ilorin. Hence, there is a need to incorporate HRQOL assessment as an adjunct outcome measure after PTB treatment especially in those with the above identified risk factors.

A radiological score for the assessment of tuberculosis progression: Validation in mouse models.

The sensitivity of in vivo low-dose high-resolution micro-computed tomography imaging enables monitoring the lung damage caused by tuberculosis. Here, we propose a radiological score integrated in the experimental workflow that enables longitudinal monitoring for prospective efficacy studies in drug development programs. The score is based on an automatic measurement of total unaffected lung volume in vivo normalized for inter-subject comparison. It was validated on well-characterized progression of chronic tuberculosis in Erdman and H37Rv strains in C3HeB/FeJ-based models. We demonstrated that a decrease in the score value indicates increasing adverse effects and vice versa. The colony-forming units count confirmed the variability in the host response suggested by the score values. The correlation between changes in the mice's weight and the score is consistent with disease progression. The classification of disease extent by k-means clustering of the score values provided the definition of the lung damage severity according to the bacillus strain. The proposed score will reduce sources of bias and improve the statistical robustness of studies by the attrition of non-infected subjects or subjects with a weak immune response. Readily available quantifications allow for a fast assessment of the therapeutic potential in drug-resistant tuberculosis strains.

Mass screening for active case finding of pulmonary tuberculosis in the Russian Federation: how to save costs.

BACKGROUND: In Russia, mass chest X-ray (CXR) screening for tuberculosis (TB) is mandatory.OBJECTIVE: To compare the yield and the cost per TB case detected and the total cost of CXR screening, passive case finding and contact tracing among adolescents and adults in the Arkhangelsk Oblast, Russian Federation, 2013-2017.DESIGN: This was an analysis of costing strategies using aggregated data. Costing information was obtained from the Finance Department of the Arkhangelsk Clinical TB Dispensary, Arkhangelsk, and the Territorial Fund of Mandatory Medical Insurance, Arkhangelsk, Russian Federation.RESULTS: TB cases were detected using CXR screening (n = 684, 46%), contact tracing (n = 61, 4%) and passive case finding (n = 743, 46%). The number of cases detected using CXR screening, contact tracing and passive case finding was respectively 28,753 and 960/100 000. The mean costs/test were respectively US$3.54 (US$12 541/case), US$20.28 (US$2693/case) and US$11.85 (US$1235/case) using CXR screening, contact tracing and passive case finding The number of cases/100 000 in targeted groups was as follows: HIV-positive persons, 645; homeless persons, 461; and migrants, 441. The cost/TB case detected was respectively US$549, US$768 and US$803.CONCLUSION: Mass CXR screening (excluding HIV-positive, migrant and homeless populations) has low yield and high cost per TB case detected. It should be stopped and resources should instead be used to strengthen the screening of targeted high-risk groups, contacts and passive case finding.

Organ-specific dose coefficients derived from Monte Carlo simulations for historical (1930s to 1960s) fluoroscopic and radiographic examinations of tuberculosis patients.

This work provides dose coefficients necessary to reconstruct doses used in epidemiological studies of tuberculosis patients treated from the 1930s through the 1960s, who were exposed to diagnostic imaging while undergoing treatment. We made use of averaged imaging parameters from measurement data, physician interviews, and available literature of the Canadian Fluoroscopy Cohort Study and, on occasion, from a similar study of tuberculosis patients from Massachusetts, United States, treated between 1925 and 1954. We used computational phantoms of the human anatomy and Monte Carlo radiation transport methods to compute dose coefficients that relate dose in air, at a point 20 cm away from the source, to absorbed dose in 58 organs. We selected five male and five female phantoms, based on the mean height and weight of Canadian tuberculosis patients in that era, for the 1-, 5-, 10-, 15-year old and adult ages. Using high-performance computers at the National Institutes of Health, we simulated 2,400 unique fluoroscopic and radiographic exposures by varying x-ray beam quality, field size, field shuttering, imaged anatomy, phantom orientation, and computational phantom. Compared with previous dose coefficients reported for this population, our dosimetry system uses improved anatomical phantoms constructed from computed tomography imaging datasets. The new set of dose coefficients includes tissues that were not previously assessed, in particular, for tissues outside the x-ray field or for pediatric patients. In addition, we provide dose coefficients for radiography and for fluoroscopic procedures not previously assessed in the dosimetry of this cohort (i.e. pneumoperitoneum and chest aspirations). These new dose coefficients would allow a comprehensive assessment of exposures in the cohort. In addition to providing newly derived dose coefficients, we believe the automation and methods developed to complete these dosimetry calculations are generalizable and can be applied to other epidemiological studies interested in an exposure assessment from medical x-ray imaging. These epidemiological studies provide important data for assessing health risks of radiation exposure to help inform the current system of radiological protection and efforts to optimize the use of radiation in medical studies.

Comparison of clinical and cost-effectiveness of two strategies using mobile digital x-ray to detect pulmonary tuberculosis in rural India.

BACKGROUND: Medanta - The Medicity, a multi-super specialty corporate hospital in Gurugram, Haryana launched a "TB-Free Haryana" Campaign; mobile van equipped with a digital CXR machine to screen patients with presumptive Tuberculosis (TB). OBJECTIVES: In this study, we aimed to assess the (1) yield and cost analysis of two strategies using mobile digital x-ray to detect Pulmonary TB in rural Haryana. METHODS: An observational study was conducted on all individuals screened by either of the two case finding strategies using a mobile x-ray unit (MXU) mounted on a mobile van in District Mewat, Haryana during Jan-March 2016. RESULTS: Strategy 1: Out of 121 smear negative cases, x-rays were suggestive of TB in 39(32%), of which 24 were started on TB treatment. Cost of identifying a smear negative TB was US$ 32. Strategy 2: Out of 596 presumptive TB, chest x-rays were suggestive of TB in 108 (18%), of which 67 were started on TB treatment (56 were smear negative TB). Cost of detecting any case of TB was US$ 08 (1 USD = 64 INR). CONCLUSION: The study reports a new initiative within a PPM model to improve the diagnosis of PTB by filling the gap in the current diagnostic infrastructure. We believe there is potential for replication of strategy 2 model in other states, although further evidence is required.

Value of chest X-ray in TB diagnosis in HIV-infected children living in resource-limited countries: the ANRS 12229-PAANTHER 01 study.

OBJECTIVE: To evaluate inter-reader agreement and diagnostic accuracy of chest radiography (CXR) in the diagnosis of tuberculosis (TB) in children with human immunodeficiency virus (HIV) infection. DESIGN: HIV-infected children with clinically suspected TB were enrolled in a prospective study conducted in Burkina Faso, Cambodia, Cameroon and Viet Nam from April 2010 to December 2014. Three readers-a local radiologist, a paediatric pulmonologist and a paediatric radiologist-independently reviewed the CXRs. Inter-reader agreement was then assessed using the κ coefficient. Diagnostic accuracy of CXR was assessed in culture-confirmed cases and controls. RESULTS: A total of 403 children (median age 7.3 years, interquartile range 3.5-9.7; 49.6% males) were enrolled. Inter-reader agreement was as follows: between local radiologist and paediatric pulmonologist, κ = 0.36 (95%CI 0.27-0.45); local radiologist and paediatric radiologist, κ = 0.16 (95%CI 0.08-0.24); and paediatric pulmonologist and paediatric radiologist, κ = 0.30 (95%CI 0.21-0.40). Among 51 cases and 151 controls, after a consensus, CXR had a sensitivity of 71.4% (95%CI 58.8-84.1) and a specificity of 50.0% (95%CI 41.9-58.1). Alveolar opacities and enlarged lymph nodes on CXR had limited specificity for TB (64.7% and 70.2%, respectively). Miliary and/or nodular opacities patterns on CXR were more specific to TB (specificity 94.3%). CONCLUSION: CXR showed poor-to-fair inter-reader agreement and limited diagnostic accuracy for TB in HIV-infected children, likely due to comorbidities. Radiological criteria for this specific population require further investigation.

Assessment of airway compression on chest radiographs in children with pulmonary tuberculosis.

BACKGROUND: Because small, pliable paediatric airways are easily compressed by enlarged lymph nodes, detection of radiographic airway compression might be an objective criterion for diagnosing pulmonary tuberculosis. OBJECTIVE: To investigate the frequency and inter-observer agreement of airway compression on chest radiographs in children with pulmonary tuberculosis compared to those with a different lower respiratory tract infection. MATERIALS AND METHODS: Chest radiographs of children with suspected pulmonary tuberculosis were read by two readers according to a standardised format and a third reader when there was disagreement. Radiographs of children with proven pulmonary tuberculosis were compared to those with a different lower respiratory tract infection. We evaluated frequency and location of radiographic airway compression. Findings were correlated with human immunodeficiency virus (HIV) status and age. We assessed inter-observer agreement using kappa statistics. RESULTS: We reviewed radiographs of 505 children (median age 25.9 months, interquartile range [IQR] 14.3-62.2). Radiographic airway compression occurred in 54/188 (28.7%) children with proven pulmonary tuberculosis and in 24/317 (7.6%) children with other types of lower respiratory tract infection (odds ratio [OR] 4.9; 95% confidence interval [CI] 2.9-8.3). A higher frequency of radiographic airway compression occurred in infants (22/101, or 21.8%) compared to older children (56/404, or 13.9%; OR 1.7; 95% CI 1.0-3.0). We found no association between airway compression and HIV infection. Inter-observer agreement ranged from none to fair (kappa of 0.0-0.4). CONCLUSION: There is a strong association between airway compression on chest radiographs and confirmed pulmonary tuberculosis. However this finding's clinical use as an objective criterion for diagnosis of pulmonary tuberculosis in children is limited by poor inter-observer agreement.

MRI as indicator of pulmonary tuberculosis activity: from morphological to molecular level assessment - a case report.

We present the case of an adult patient with active post-primary pulmonary tuberculosis (TB) and discuss specific morphological and textural aspects found at high-field magnetic resonance imaging (MRI) of the lung. The 42-year-old man, heavy smoker, undertook a routine employment medical examination and was admitted to a referral pulmonology and TB center due to the abnormal findings seen on his chest radiography. The patient presented nonspecific symptoms, bilateral bronchial breath at pulmonary auscultation, inflammatory syndrome on the laboratory blood tests and positive sputum smears for acid-fast bacilli, which together with the typical aspect on the chest radiography lead to a diagnosis of post-primary pulmonary TB and administration of specific medication. To exclude a possible lung cancer and to reevaluate the extent of the disease, computed tomography and magnetic resonance imaging of the lung were performed. The magnetic resonance examination showed, with an accuracy similar to that of computed tomography, the morphology of active post-primary parenchymal TB lesions, as depicted on the T2-weighted acquisition. Moreover, the T1-weighted sequence using iterative decomposition allowed the assessment of both lipid and caseous pneumonia. To the best of our knowledge, this is the first reported case to assess post-primary pulmonary TB using high field MRI equipment, with an analysis from a morphological to a molecular level. By using a fast two-sequence protocol, both morphological, through T2-weighted acquisition, and textural information such as fat content, using dedicated T1-weighted sequence, can be obtained.

Use of low-dose computed tomography to assess pulmonary tuberculosis among healthcare workers in a tuberculosis hospital.

BACKGROUND: According to the World Health Organization, China is one of 22 countries with serious tuberculosis (TB) infections and one of the 27 countries with serious multidrug-resistant TB strains. Despite the decline of tuberculosis in the overall population, healthcare workers (HCWs) are still at a high risk of infection. Compared with high-income countries, the TB prevalence among HCWs is higher in low- and middle-income countries. Low-dose computed tomography (LDCT) is becoming more popular due to its superior sensitivity and lower radiation dose. However, there have been no reports about active pulmonary tuberculosis (PTB) among HCWs as assessed with LDCT. The purposes of this study were to examine PTB statuses in HCWs in hospitals specializing in TB treatment and explore the significance of the application of LDCT to these workers. METHODS: This study retrospectively analysed the physical examination data of healthcare workers in the Beijing Chest Hospital from September 2012 to December 2015. Low-dose lung CT examinations were performed in all cases. The comparisons between active and inactive PTB according to the CT findings were made using the Pearson chi-square test or the Fisher's exact test. Comparisons between the incidences of active PTB in high-risk areas and non-high-risk areas were performed using the Pearson chi-square test. Analyses of active PTB were performed according to different ages, numbers of years on the job, and the risks of the working areas. Active PTB as diagnosed by the LDCT examinations alone was compared with the final comprehensive diagnoses, and the sensitivity and positive predictive value were calculated. RESULTS: A total of 1 012 participants were included in this study. During the 4-year period of medical examinations, active PTB was found in 19 cases, and inactive PTB was found in 109 cases. The prevalence of active PTB in the participants was 1.24%, 0.67%, 0.81%, and 0.53% for years 2012 to 2015. The corresponding incidences of active PTB among the tuberculosis hospital participants were 0.86%, 0.41%, 0.54%, and 0.26%. Most HCWs with active TB (78.9%, 15/19) worked in the high-risk areas of the hospital. There was a significant difference in the incidences of active PTB between the HCWs who worked in the high-risk and non-high-risk areas (odds ratio [OR], 14.415; 95% confidence interval (CI): 4.733 - 43.896). Comparisons of the CT signs between the active and inactive groups via chi-square tests revealed that the tree-in-bud, cavity, fibrous shadow, and calcification signs exhibited significant differences (P = 0.000, 0.021, 0.001, and 0.024, respectively). Tree-in-bud and cavity opacities suggest active pulmonary tuberculosis, whereas fibrous shadow and calcification opacities are the main features of inactive pulmonary tuberculosis. Comparison with the final comprehensive diagnoses revealed that the sensitivity and positive predictive value of the diagnoses of active PTB based on LDCT alone were 100% and 86.4%, respectively. CONCLUSIONS: Healthcare workers in tuberculosis hospitals are a high-risk group for active PTB. Yearly LDCT examinations of such high-risk groups are feasible and necessary.

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.

Impact of x-ray screening programmes for active tuberculosis in homeless populations: a systematic review of original studies.

BACKGROUND: Tuberculosis prevalence is generally low in industrialized countries, but many cities now operate surveillance programmes to actively screen for tuberculosis in known risk groups including homeless people. While several studies have reported on individual screening programmes, this study is the first known systematic review specifically looking at chest x-ray screening programmes for tuberculosis in homeless populations. METHODS: Systematic review of relevant studies published in the last 20 years using the PRISMA checklist. RESULTS: Fourteen studies were reviewed: 12 cross-sectional studies, 1 retrospective cohort study and 1 'data-linkage' study. The studies were heterogenous in terms of the objectives, measured outcomes and methodological quality. Active tuberculosis prevalence was found to be higher in homeless populations and screening programmes appear to identify tuberculosis earlier, reduce prevalence and transmission, and increase treatment compliance. CONCLUSIONS: Active x-ray surveillance programmes in homeless communities appear to be cost-effective in reducing prevalence within the homeless population particularly in related strains and may have some benefits over passive finding. While there is a need for high-quality research to further assess the impact of these programmes, this study has outlined the benefits and limitations of existing programmes and included recommendations to achieve maximum coverage, uptake and cost-benefit.

Assessment of previous tuberculosis status using questionnaires, chest X-rays and computed tomography scans.

SETTING: Accurate diagnosis of previous pulmonary tuberculosis disease (PPTB) status is important clinically and in research. Reliable records of bacteriologically confirmed tuberculosis (TB) are frequently unavailable. OBJECTIVES: To evaluate the use of questionnaires and chest imaging to determine PPTB status in a high TB prevalence population. DESIGN: PPTB status was assessed using two questionnaires, chest X-ray (CXR) and high-resolution chest computed tomography (CT) scans reported by experienced readers. The study population comprised adults aged >40 years diagnosed with obstructive lung disease in a community-based prevalence survey. RESULTS: The Burden of Obstructive Lung Disease (BOLD) questionnaire and a second comprehensive questionnaire (PTbQ) provided a history of PPTB in respectively 38% (n = 41) and 36.4% (n = 39) of 107 participants. On CXR, 43.3% (45/104) had evidence of PPTB, with good inter-reader agreement (κ = 0.73). Changes compatible with PPTB were identified on chest CT in 68.3% (71/104) of the subjects. Questionnaire and CXR had negative predictive values for PPTB of 48% and 47%, respectively, compared to a composite definition. CONCLUSION: Both questionnaire and CXR markedly underestimate the prevalence of previous TB in patients with chronic obstructive pulmonary disease. The combination of a structured questionnaire and CT scan is more useful when a diagnosis of PPTB needs to be ruled out.

Initial assessment of image quality for low-dose PET: evaluation of lesion detectability.

In the context of investigating the potential of low-dose PET imaging for screening applications, we developed methods to assess small lesion detectability as a function of the number of counts in the scan. We present here our methods and preliminary validation using tuberculosis cases. FDG-PET data from seventeen patients presenting diffuse hyper-metabolic lung lesions were selected for the study, to include a wide range of lesion sizes and contrasts. Reduced doses were simulated by randomly discarding events in the PET list mode, and ten realizations at each simulated dose were generated and reconstructed. The data were grouped into 9 categories determined by the number of included true events, from >40 M to <250 k counts. The images reconstructed from the original full statistical set were used to identify lung lesions, and each was, at every simulated dose, quantified by 6 parameters: lesion metabolic volume, lesion-to-background contrast, mean lesion tracer uptake, standard deviation of activity measurements (across realizations), lesion signal-to-noise ratio (SNR), and Hotelling observer SNR. Additionally, a lesion-detection task including 550 images was presented to several experienced image readers for qualitative assessment. Human observer performances were ranked using receiver operating characteristic analysis. The observer results were correlated with the lesion image measurements and used to train mathematical observer models. Absolute sensitivities and specificities of the human observers, as well as the area under the ROC curve, showed clustering and performance similarities among images produced from 5 million or greater counts. The results presented here are from a clinically realistic but highly constrained experiment, and more work is needed to validate these findings with a larger patient population.