Tuberculin Skin Test Screening Research Articles

Sa1266 Interferon-γ Release Assay Versus Tuberculin Skin Test in Patients With Moderate-to-Severely Active Ulcerative Colitis: Results From the PURSUIT UC Program

Objective: To report results of an interferonΥ release assay (IGRA) vs standard tuberculin skin test (TST) as a screening tool for latent TB infection in patients with UC in PURSUIT. Methods: Patients with moderately to severely active UC were screened for latent TB using the standard TST and the IGRA to assess eligibility for entry into the induction studies of golimumab (PURSUIT-SC [C0524T17]and PURSUIT-IV [C0524T1]Any patient with a newly identified positive finding for TB on a diagnostic test in whom there was no evidence of active TB was permitted to enter provided appropriate treatment for latent TB was initiated before or at the time of the first dose of study agent. TST was performed according to the Mantoux method, using 5 tuberculin units (TU) of purified protein derivative (PPD) standard or 2 TU of PPD RT-23. The TST was deemed positive for latent TB infection according to the local country guidelines for defining an immunosuppressed host or, in the absence of local guidelines, according to the presence of induration >5mm. The IGRA used to screen for latent TB was the QuantiFERON-TB Gold In-Tube test. Overall IGRA and TST results were assessed. The impact of prior BCG vaccination and concomitant medication (ie corticosteroids and/or immunomodulators ) on outcome was assessed. Results: 1283 patients had both IGRA and TST screening prior to GLM treatment. Among these patients, 8.7% had at least one test yielding positive findings for latent TB, including 6.2% with positive results

Latent tuberculosis infection screening in foreign-born populations: a successful mobile clinic outreach model.

We evaluated the efficacy of a mobile medical clinic (MMC) screening program for detecting latent tuberculosis infection (LTBI) and active tuberculosis. A LTBI screening program in a MMC in New Haven, Connecticut, used medical surveys to examine risk factors and tuberculin skin test (TST) screening eligibility. We assessed clinically relevant correlates of total (prevalent; n = 4650) and newly diagnosed (incident; n = 4159) LTBI from 2003 to 2011. Among 8322 individuals, 4159 (55.6%) met TST screening eligibility criteria, of which 1325 (31.9%) had TST assessed. Similar to LTBI prevalence (16.8%; 779 of 4650), newly diagnosed LTBI (25.6%; 339 of 1325) was independently correlated with being foreign-born (adjusted odds ratio [AOR] = 8.49; 95% confidence interval [CI] = 5.54, 13.02), Hispanic (AOR = 3.12; 95% CI = 1.88, 5.20), Black (AOR = 2.16; 95% CI = 1.31, 3.55), employed (AOR = 1.61; 95% CI = 1.14, 2.28), and of increased age (AOR = 1.04; 95% CI = 1.02, 1.05). Unstable housing (AOR = 4.95; 95% CI = 3.43, 7.14) and marijuana use (AOR = 1.57; 95% CI = 1.05, 2.37) were significantly correlated with incident LTBI, and being male, heroin use, interpersonal violence, employment, not having health insurance, and not completing high school were significantly correlated with prevalent LTBI. Screening for TST in MMCs successfully identifies high-risk foreign-born, Hispanic, working, and uninsured populations and innovatively identifies LTBI in urban settings.

Relating Tuberculosis (TB) Contact Characteristics to QuantiFERON-TB-Gold and Tuberculin Skin Test Results in the Toronto Pediatric TB Clinic.

Few data relate interferon-γ-release-assay results in children to source case sputum status, the best predictor of infectiousness of tuberculosis (TB) patients. We evaluated the QuantiFERON-Gold-in-tube assay (QFT) and tuberculin skin test (TST) in children with different types of TB exposure. The TST and QFT were performed in referred TB-exposed children and adolescents who had not undergone prior TST screening (tested in parallel), and the QFT was performed in referred TST-positive individuals. Source case characteristics were obtained from referring public health units. We excluded children with known immunocompromising conditions and those known to have TB disease at the time of evaluation. For 103 patients tested in parallel, overall test agreement was very good in the Bacillus Calmette-Guerein (BCG) unimmunized contacts (κ = 0.83) and contacts of household smear-positive (HS+) cases (κ = 0.67), but test agreement was poor in those with lower-risk contact (κ = 0.34). Only 3 of 59 HS+ patients were QFT-positive and TST-negative. On multivariate analysis, a positive QFT was strongly associated with HS+ exposure (odds ratio [OR], 6.6; 95% confidence interval [CI], 2.2-20]) but not BCG; and a positive TST was associated with BCG alone. For 92 referred TST-positive individuals, the QFT was negative in 21% of HS+ contacts, 65% of lower-risk contacts (OR, 6.8; 95% CI, 1.9-25), and 82% of the patients with unknown contact history (OR, 15.5; 95% CI, 5-54). Application of the Canadian 2010 guidelines would exclude from treatment 43 (72%) of the 73 TST+, QFT- patients. For close contacts of HS+ individuals, the QFT added little sensitivity to the TST for detection of TB infection. The QFT correlated much better with exposure than the TST, especially in BCG-immunized children, and it has the greatest potential benefit for evaluation of those at lower risk of latent TB infection.

T-Cell Profiling and the Immunodiagnosis of Latent Tuberculosis Infection in Patients with Inflammatory Bowel Disease

Factors associated with performance of interferon-γ release assays (IGRA) and the tuberculin skin test (TST) in screening for latent tuberculosis infection in patients with inflammatory bowel diseases (IBD) are still poorly understood. The influence of peripheral T-cell subset counts on the results also remain unclear. Prospective single-center study in 205 patients with IBD. Latent tuberculosis infection screening included a chest radiograph, TST (retest if negative), and 2 IGRAs: QuantiFERON-TB Gold In-Tube (QFT-GIT) and TSPOT-TB (TSPOT). T-cell subpopulations were determined by flow cytometry. Twenty-one (10.2%) patients had an abnormal chest radiograph, 55 (26.8%) had a positive TST, 16 (7.8%) had a positive QFT-GIT, and 25 (12.6%) had a positive TSPOT. TST positivity was lower in patients on ≥2 immunosuppressants compared with the controls (5-aminosalicylic acid treatment) (10.4% versus 38.2%, respectively) (P = 0.0057). No other drugs influenced TST or IGRA positivity. In patients on corticosteroid treatment, anti-TNF treatment, or ≥2 immunosuppressants, IGRAs detected 10 cases of latent tuberculosis infection not identified by TST. TSPOT and QFT-GIT increased yield by 56% and 22%, respectively. No significant differences in T-cell subpopulations were found between patients with positive or negative TST or TSPOT results. However, patients with positive QFT-GIT findings had more CD8 T cells (mean, 883 ± 576 versus 484 ± 385 cells per microliter in patients with negative results) (P = 0.022). IGRAs can improve TST-based screening in patients with IBD on immunosuppressive therapy. A low CD8 count can affect QFT-GIT results. We suggest combining TSPOT and TST screening in patients with IBD on immunosuppressants.

How Methodologic Differences Affect Results of Economic Analyses: A Systematic Review of Interferon Gamma Release Assays for the Diagnosis of LTBI

IntroductionCost effectiveness analyses (CEA) can provide useful information on how to invest limited funds, however they are less useful if different analysis of the same intervention provide unclear or contradictory results. The objective of our study was to conduct a systematic review of methodologic aspects of CEA that evaluate Interferon Gamma Release Assays (IGRA) for the detection of Latent Tuberculosis Infection (LTBI), in order to understand how differences affect study results.MethodsA systematic review of studies was conducted with particular focus on study quality and the variability in inputs used in models used to assess cost-effectiveness. A common decision analysis model of the IGRA versus Tuberculin Skin Test (TST) screening strategy was developed and used to quantify the impact on predicted results of observed differences of model inputs taken from the studies identified.ResultsThirteen studies were ultimately included in the review. Several specific methodologic issues were identified across studies, including how study inputs were selected, inconsistencies in the costing approach, the utility of the QALY (Quality Adjusted Life Year) as the effectiveness outcome, and how authors choose to present and interpret study results. When the IGRA versus TST test strategies were compared using our common decision analysis model predicted effectiveness largely overlapped.ImplicationsMany methodologic issues that contribute to inconsistent results and reduced study quality were identified in studies that assessed the cost-effectiveness of the IGRA test. More specific and relevant guidelines are needed in order to help authors standardize modelling approaches, inputs, assumptions and how results are presented and interpreted.

Screening employees of services for homeless individuals in Montréal for tuberculosis infection

The results of a tuberculin skin test (TST) screening program offered to employees of services for homeless people in Montréal from 1998 to 2005 were analyzed to assess the occupational risk of tuberculosis (TB) infection. Employees with no known contact with TB were selected among volunteer participants. They were followed in two dynamic cohorts: individuals with a negative two-step baseline TST (cohort A) and individuals with a negative single baseline TST (cohort B). We estimated the prevalences of initial positive TST, boosting effect, and conversion rate. The average age of the workers was 38.9 years. The prevalence of an initial positive TST was 12.9%. A booster effect was observed in 5.1% of workers who completed a two-step TST. The incidence of conversion was 2.3/100 person-years for cohort A (n=93) and 3.5/100 person-years for cohort B (n=221). The incidence of conversion was not significantly associated with any of the demographics or workplace factors investigated. Our findings are comparable to the rates reported among community workers, whose risk is higher than the average health worker. This suggests that there are occasional unidentified contagious cases among the homeless individuals of participating institutions.

Tuberculin Skin Test, Chest Radiography and Contact Screening in Young Children

Tuberculin Skin Test, Chest Radiography and Contact Screening in Young Children

Interferon‐γ release assay versus tuberculin skin test prior to treatment with golimumab, a human anti–tumor necrosis factor antibody, in patients with rheumatoid arthritis, psoriatic arthritis, or ankylosing spondylitis

To evaluate the performance of an interferon-γ release assay (IGRA) versus the standard tuberculin skin test (TST) as a screening tool for latent tuberculosis (TB) infection prior to the initiation of anti-tumor necrosis factor therapy in patients with autoimmune inflammatory diseases. This integrated analysis involved screening of patients with rheumatoid arthritis, those with psoriatic arthritis, and those with ankylosing spondylitis from phase III trials of golimumab. The IGRA used to screen for latent TB was the QuantiFERON-TB Gold In-Tube test. In this pooled analysis, 2,282 patients underwent both IGRA and TST screening prior to golimumab treatment. Among these patients, 13.8% had at least one test yielding positive findings for latent TB, including 9.4% with positive results by TST, 7.0% with positive results by IGRA, and 2.6% with positive results on both tests. The rate of indeterminate results for TB on IGRA was 1.8%. Agreement between the TST and IGRA results, measured by the kappa coefficient, was 0.22 (95% confidence interval 0.157-0.279; P=0.021). Among the patients with positive IGRA findings, 36.9% had positive TST findings. Among the patients with positive TST findings, 27.4% had positive IGRA findings. Overall, 781 (34.2%) of the 2,282 patients had previously received the bacillus Calmette-Guérin (BCG) vaccine; among this vaccinated group, the rate of positivity for latent TB by TST was 15.2% (119 of 781), compared to a rate of positivity of 9.1% (71 of 781) by IGRA (P=0.0002). Among patients who had not received the BCG vaccine, the rate of positivity by TST was 5.0% (62 of 1,248) and the rate of positivity by IGRA was 5.8% (72 of 1,248) (P=0.3745). When the IGRA was repeated in patients whose results were initially indeterminate, the rate of indeterminate IGRA findings for latent TB was much lower than has been previously reported. In the absence of a true gold standard test for latent TB infection, results of this comparison of IGRA and TST in a large cohort of patients with rheumatic diseases suggest that the IGRA provides greater specificity and possibly greater sensitivity than the TST.

Cost Effectiveness of Interferon-Gamma Release Assay for School-Based Tuberculosis Screening

To assess the cost effectiveness of school-based tuberculosis (TB) screening using QuantiFERON®-TB Gold In-Tube (QFT) versus the tuberculin skin test (TST) and chest x-ray examination (CXR). We constructed Markov models of first-year high-school and university students, using a societal perspective, and followed them up until the age of 80 years. Three strategies (QFT, TST, and CXR) were modeled. All costs and clinical benefits were discounted at a fixed annual rate of 3%. In the base-case analyses of 16-year-old high-school students and 19-year-old university students, the QFT strategy yielded the greatest benefits at the lowest cost [in year 2009 values] (16-year-olds: $US627.89, 29.69835 quality-adjusted life-years [QALYs]; 19-year-olds: $US646.04, 29.15361 QALYs), compared with the TST strategy (16-year-olds: $US943.50, 29.69767 QALYs; 19-year-olds: $US998.62, 29.15288 QALYs) and the CXR strategy (16-year-olds: $US7286.24, 29.69532 QALYs; 19-year-olds: $US7305.19, 29.14911 QALYs). On one-way sensitivity analyses, the bacillus Calmette-Guérin (BCG) vaccination rate was not sensitive to the TST strategy. On probabilistic sensitivity analysis, the QFT strategy was the most cost effective, with a willingness-to-pay level of $US50 000/QALY gained. The QFT strategy provided the greatest benefits at the lowest cost for school-based TB screening. There appears to be little role for TST or CXR in screening of school populations. Current practices using either TST or CXR screening should be reconsidered on the basis of cost effectiveness.

Street-outreach Improves Detection but not Referral for Drug Users with Latent Tuberculosis, New York City

Street outreach in two New York City communities, Harlem and the South Bronx, between May 2001 and March 2003, provided tuberculin skin test (TST) screening to illicit drug users outside the traditional health care system. Persons who used heroin, cocaine, and/or crack were offered a TST, incentives to return for TST reading, and further evaluation if TST was positive. Of 809 participants, 530 (66%) accepted a TST and 81% (429/530) returned for TST reading. Of 429 participants, 40 (9%) were TST positive. Participants found TST positive did not differ from those found TST negative in previous drug user treatment or drug use practices including snorting heroin, sniffing cocaine, smoking crack, and injecting drugs of any kind. Of the 40 participants found TST positive, the 21 who tested TST positive for the first time were more likely to be male (p = .03) and noninjectors (p = .02), than the 19 who had tested TST positive in the past. Only two newly identified persons pursued follow-up care. Street recruitment expanded testing. Better follow-up strategies are needed. The study's limitations are noted.

Priorities for Screening and Treatment of Latent Tuberculosis Infection in the United States

To improve the effectiveness of tuberculosis (TB) control programs in the United States by identifying cost-effective priorities for screening for latent tuberculosis infection (LTBI). To estimate the cost-effectiveness of LTBI screening using the tuberculin skin test (TST)and interferon-g release assays (IGRAs). A Markov model of screening for LTBI with TST and IGRA in risk-groups considered in current LTBI screening guidelines. In all risk-groups, TST and IGRA screening resulted in increased mean life expectancy, ranging from 0.03–0.24 life-months per person screened. IGRA screening resulted in greater life expectancy gains than TST. Screening always cost more than not screening, but IGRA was cost-saving compared with TST in some groups. Four patterns of cost-effectiveness emerged, related to four risk categories. (1) Individuals at highest risk of TB reactivation (close contacts and those infected with HIV): the incremental cost-effectiveness ratio (ICER) of IGRA compared with TST was less than $100,000 per quality-adjusted life year (QALY) gained. (2) The foreign-born: IGRA was cost-saving compared with TST and cost-effective compared with no screening (ICER ,$100,000 per QALY gained). (3) Vulnerable populations (e.g., homeless, drug user, or former prisoner): the ICER of TST screening was approximately $100,000–$150,000 per QALY gained, but IGRA was not cost-effective. (4) Medical comorbidities (e.g., diabetes): the ICER of screening with TST or IGRA was greater than $100,000 per QALY. LTBI screening guidelines could make progress toward TB elimination by prioritizing screening for close contacts, those infected with HIV, and the foreign-born regardless of time living in the United States. For these groups, IGRA screening was more cost-effective than TST screening.

Use of the QuantiFERON‐TB Gold interferon‐gamma release assay for screening transplant candidates: a single‐center retrospective study

Tuberculosis (TB) reactivation is a rare but significant complication of organ transplantation, and screening of all transplant candidates for latent infection is recommended with either an interferon-γ release assay (IGRA) or tuberculin skin test (TST). After institutional review board approval, we retrospectively collected data to describe the yield of transplant candidate screening using the QuantiFERON-TB Gold (QFT) and QuantiFERON-TB Gold In-Tube (QFT-IT) assays since the institution of TB screening in 2008 and the epidemiology of all cases of post-transplant TB in our institution since 2004. A total of 2392 patients were screened with either the QFT or QFT-IT assay through October 2009; 245 (10.2%) tested positive and 206 (8.6%) were indeterminate. Of those with positive results, 107 (43.7%) were foreign born and most of the remainder had prior TB exposures. Of the tests performed at a reference lab, 29% were indeterminate, whereas 14% were indeterminate using our in-house lab. The majority of indeterminate results were seen in liver transplant candidates (40.6% vs. 11.8% in non-liver candidates). Three of 694 (0.43%) screened patients who underwent transplantation developed TB post transplant. Post-transplant TB occurs at a low rate with universal IGRA-based candidate screening, which is comparable to studies using TST screening.

Interferon-γ releasing assay versus tuberculin skin testing for latent tuberculosis infection in targeted screening programs for high risk immigrants

Recent immigrants from developing countries (<2 years since immigration) are at very high risk of active TB disease due to reactivation of latent infections acquired in the country of origin. In industrialized low-incidence TB countries targeted testing programs for high risk groups could allow the detection of latently infected persons who would likely benefit from a course of preventive treatment. In this study we evaluated the tuberculin skin test (TST) and interferon-gamma enzyme-linked immunosorbent assay (QuantiFERON TB-gold in tube, QFT-IT) strategies for TB infection screening programs in recent immigrants from highly endemic countries. This is a prospective cross-sectional study. Paired tests performed in 1,130 immigrants attending an outpatient ward, between 2005 and 2007 for any health problem were evaluated by intention-to-treat (ITT) and per-protocol (PP) analysis for efficiency and efficacy of screening program. Positive TST and QFT-IT were observed in 36.04 versus 29.82% (ITT) and in 45.27 versus 30.22% (PP) respectively. A higher drop-out rate was observed for TST (20.35 vs. 1.33%) (p < 0.0001). Second level assessment was accepted by half of the TST positive patients. Overall agreement rate between 887 paired tests was fair (k = 0.38). Higher k values were observed for higher TB prevalence rate in the country of origin (k = 0.43), for TST induration diameters >20 mM (k = 0.47), in subjects aged 40-50 years (k = 0.41) and in unvaccinated persons (k = 0.40). In a multiple logistic regression model continent of origin, class of TB prevalence in the country of origin and contacts with TB patients were found to be significantly associated with the probability of TST and QFT-IT positive result. Low education levels were associated only to an increased risk of TST positive results. The drawback of the TST screening strategy in recent immigrants from highly endemic countries is due to low sensitivity/specificity of the test and to high drop-out rate with an overall significant lowering in strategy efficacy/efficiency. The higher QFT-IT specificity prevents unnecessary overload of the health care system and, although more expensive, might represent a cost-effective alternative to TST in targeted screening programs directed to high risk populations.

Comparison of Tuberculin Skin Testing Reactivity in Opioid-Dependent Patients Seeking Treatment with Methadone versus Buprenorphine: Policy Implications for Tuberculosis Screening

Background: Buprenorphine's availability in primary care settings offers increased access to treatment and linkage to primary care for opioid-dependent patients. Currently, tuberculin skin testing (TST) is recommended for patients enrolling in methadone maintenance treatment (MMT), but not for those enrolling in buprenorphine maintenance treatment (BMT). Objectives: To compare TST screening results in enrollees in BMT and MMT programs and assess the correlates of TST positivity among these subjects. Methods: A cross-sectional analysis of a retrospective cohort study was conducted to compare concurrent TST results among contemporaneously matched groups of MMT and BMT patients in the same community. Results: TST positivity was ∼9% in both MMT and BMT settings (p = .27). Increased TST positivity was associated with being Black (AOR = 3.53, CI = 1.28–9.77), Hispanic (AOR = 3.11, CI = 1.12–8.60), and having higher education (AOR = 3.01, CI = 1.20–7.53). Conclusions: These results confirm a similar high prevalence of TST positivity in opioid-dependent patients enrolling in MMT and BMT programs. Racial and ethnic health disparities remain associated with TST positivity, yet a relationship between higher education and tuberculosis requires further investigation. Scientific significance: These data suggest the importance of incorporating TST screening in emerging BMT programs as a mechanism to provide increased detection and treatment of tuberculosis infection in opioid-dependent patient populations.

School based screening for tuberculosis infection in Norway: comparison of positive tuberculin skin test with interferon-gamma release assay

BackgroundIn Norway, screening for tuberculosis infection by tuberculin skin test (TST) has been offered for several decades to all children in 9th grade of school, prior to BCG-vaccination. The incidence of tuberculosis in Norway is low and infection with M. tuberculosis is considered rare. QuantiFERON®TB Gold (QFT) is a new and specific blood test for tuberculosis infection. So far, there have been few reports of QFT used in screening of predominantly unexposed, healthy, TST-positive children, including first and second generation immigrants. In order to evaluate the current TST screening and BCG-vaccination programme we aimed to (1) measure the prevalence of QFT positivity among TST positive children identified in the school based screening, and (2) measure the association between demographic and clinical risk factors for tuberculosis infection and QFT positivity.MethodsThis cross-sectional multi-centre study was conducted during the school year 2005–6 and the TST positive children were recruited from seven public hospitals covering rural and urban areas in Norway. Participation included a QFT test and a questionnaire regarding demographic and clinical risk factors for latent infection. All positive QFT results were confirmed by re-analysis of the same plasma sample. If the confirmatory test was negative the result was reported as non-conclusive and the participant was offered a new test.ResultsAmong 511 TST positive children only 9% (44) had a confirmed positive QFT result. QFT positivity was associated with larger TST induration, origin outside Western countries and known exposure to tuberculosis. Most children (79%) had TST reactions in the range of 6–14 mm; 5% of these were QFT positive. Discrepant results between the tests were common even for TST reactions above 15 mm, as only 22 % had a positive QFT.ConclusionThe results support the assumption that factors other than tuberculosis infection are widely contributing to positive TST results in this group and indicate the improved specificity of QFT for latent tuberculosis. Our study suggests a very low prevalence of latent tuberculosis infection among 9th grade school children in Norway. The result will inform the discussion in Norway of the usefulness of the current TST screening and BCG-policy.

Tuberculosis Control in a Large Urban Jail

This study evaluated adherence to tuberculosis control guidelines, published by the Centers for Disease Control and Prevention in 1996, in a large urban jail. Jails are a critical locale because of high risk for tuberculosis transmission in a congregate setting. Symptom screening at intake into the facility was systematically observed. Medical records were reviewed to measure timing of tuberculin skin testing (TST) and chest radiograph (CXR) screening. Isolation records were examined for airborne infectious isolation practices. Contact investigation practices were evaluated for ease of data retrieval and adherence to CDC guidelines. A TB symptom screening question was asked correctly during 28/97 of intake health interviews. Median time from intake to TST was 3 days for men and 2 days for women. Median time from referral to CXR was 2 days for men and 7 days for women. Delays were noted in diagnostic testing of 51 detainees isolated for suspected TB. Contact investigations lacked comprehensive procedures, data collection forms, and databases for managing information. Findings were used to refine protocols for TB control. This evaluation illustrated the need for ongoing assessment of adherence to TB control protocols in short-term correctional settings to prevent the spread of TB.

Evaluation of a large-scale tuberculosis contact investigation in the Netherlands

The aim of the present study was to evaluate yield and effectiveness of a large-scale contact investigation around a supermarket employee with infectious tuberculosis. Supermarket customers were screened by tuberculin skin test (TST) and/or radiography, depending on individual characteristics. The number of recent infections was estimated based on historical reference data after correction for false-positive TST results. TST screening of 15,518 subjects yielded 12 cases of tuberculosis disease as a direct result of the investigation (1,293 screenings per case identified). Radiographical screening of 5,945 subjects yielded no cases. There were 359 (2.6%) positive TSTs; 117 (34%) were estimated to be due to recent exposure. The number of customers screened in order to find one case of recent infection was 114, varying from 43 for customers who visited the supermarket twice per week or more, to 4,148 for customers who visited less than once per month. In conclusion, although this patient probably transmitted Mycobacterium tuberculosis to at least 117 customers, the contact investigation was inefficient, as large numbers of customers had to be screened and the majority of identified tuberculosis infections were probably not related to the index case. The efficiency could have been improved by omitting radiographical screening and limiting tuberculin skin test screening to customers who reported frequent supermarket visits.

Cost-effectiveness of Interferon-γ Release Assay Screening for Latent Tuberculosis Infection Treatment in Germany

To assess the cost-effectiveness of the new QuantiFERON-TB Gold In-Tube (QFT-G) [Cellestis; Carnegie, VIC, Australia] assay for screening and treating of persons who have had close contact with tuberculosis (TB) patients and are suspected of having latent tuberculosis infection (LTBI) [hereafter called close-contacts] in Germany. The health and economic outcomes of isoniazid treatment of 20-year-old close-contacts were compared in a Markov model over a period of 20 years, using two different cutoff values for the tuberculin skin test (TST), the QFT-G assay alone, or the QFT-G assay as a confirmatory test for the TST results. QFT-G assay-based treatment led to cost savings of $542.9 and 3.8 life-days gained per LTBI case. TST-based treatment at a 10-mm induration size cutoff gained $177.4 and 2.0 life-days gained per test-positive contact. When the cutoff induration size for the TST was reduced to 5 mm, the incremental cost-effectiveness ratio fell below the willingness-to-pay threshold ($30,170 per life-years gained) but resulted in unnecessary treatment of 77% of contacts owing to false-positive TST results. Combination with the 5-mm induration size TST cutoff value compared to the results of the QFT-G assay alone reduced the total costs per 1,000 contacts by 1.8% to $222,869. The number treated to prevent 1 TB case was 22 for the two QFT-G assay-based procedures, 40 for the TST at a cutoff induration size of 10 mm, and 96 for the TST at a cutoff induration size of 5 mm. When the sensitivity rates of the TST and the QFT-G assay were compounded, the QFT-G assay strategy alone was slightly less costly (0.6%) than the two-step approach. Using the QFT-G assay, but especially combining the QFT-G assay following the TST screening of close-contacts at a cutoff induration size of 5 mm before LTBI treatment is highly cost-effective in reducing the disease burden of TB.

Tuberculin skin test positivity in pediatric allogeneic BMT recipients and donors in Turkey

The preliminary study was performed to determine the frequency of tuberculin skin test (TST) positivity among 26 patients and their donors screened by TST to investigate whether tuberculin positivity of a recipient or donor influenced the rate of tuberculosis disease, transplant-related events, and to evaluate the effectiveness of isoniazide (INAH) prophylaxis administered to those with positive TST. The frequency of TST positivity was 23% (n = 6) among recipients and also 23% (n = 6) among donors. Two recipients and five donors with positive TST received INAH prophylaxis for six months. Our use of INAH prophylaxis in transplant patients was very conservative because of the risk of drug interaction. The transplantation procedure was not postponed for either recipient or donor TST positivity. Despite the high frequency of tuberculosis in our country, we have not detected any case of tuberculosis in our center, either among the purified protein derivative-screened (n = 26) or non-screened (n = 128) patients except for disseminated tuberculosis infection because of BCG vaccination in two patients with severe combined immunodeficiency. In conclusion, TST positivity in either recipient or donor may not be a contraindication for bone marrow transplantation and the procedure may not be postponed. Pretransplantation TST screening may be needed in countries where tuberculosis is common in the general population.

Room size is the major determinant for tuberculin conversion in health care workers exposed to a multidrug-resistant tuberculosis patient

Transmission of Mycobacterium tuberculosis (MTB) to health care workers (HCWs) still represents a public health concern. A total of 71 obstetric workers underwent contact tracing after recent workplace exposure to a highly infectious multidrug-resistant tuberculosis patient [i.e., index case (IC)]. Aim of the study was to identify the main exposure predictors for the risk of conversion through evaluation of tuberculin screening results. HCWs were investigated by a questionnaire (community, occupational, IC exposure risk factors) and tuberculin skin test screening. Conversion was detected in 5 (8%) of the 63 exposed workers and was not associated with either community or previous work-related risk factors. According to risk assessment, tuberculin conversion was related to neither amount time of exposure, workshifts, nor number of contacts. Conversely, an exposure to the IC in different hospital rooms was found significantly different among converters compared to non-converters (chi (2), P = 0.004). In particular, conversion was associated with exposure in two (obstetric emergency room, ambulatory discharge) out of the nine contact environments. Tuberculin conversion rates were associated with the room cubations of the exposure environments (chi (2) for trend, P < 0.01) and with worker age. In a logistic regression model adjusted for age, the lower room cubation was found the strongest predictor for tuberculin conversion (OR = 2.46, P = 0.02). The study shows that the factors affecting airborne mycobacterial dose (patient infectiousness, low sized confined rooms) were the major determinants for MTB transmission after a brief exposure to a highly infectious TB case.