Latent Tuberculosis Infection Cases Research Articles

Exposure to second-hand smoke and the risk of tuberculosis in children and adults: a systematic review and meta-analysis of 18 observational studies.

BackgroundAccording to WHO Global Health Estimates, tuberculosis (TB) is among the top ten causes of global mortality and ranks second after cardiovascular disease in most high-burden regions. In this systematic review and meta-analysis, we investigated the role of second-hand smoke (SHS) exposure as a risk factor for TB among children and adults.Methods and FindingsWe performed a systematic literature search of PubMed, Embase, Scopus, Web of Science, and Google Scholar up to August 31, 2014. Our a priori inclusion criteria encompassed only original studies where latent TB infection (LTBI) and active TB disease were diagnosed microbiologically, clinically, histologically, or radiologically. Effect estimates were pooled using fixed- and random-effects models. We identified 18 eligible studies, with 30,757 children and 44,432 adult non-smokers, containing SHS exposure and TB outcome data for inclusion in the meta-analysis. Twelve studies assessed children and eight studies assessed adult non-smokers; two studies assessed both populations. Summary relative risk (RR) of LTBI associated with SHS exposure in children was similar to the overall effect size, with high heterogeneity (pooled RR 1.64, 95% CI 1.00–2.83). Children showed a more than 3-fold increased risk of SHS-associated active TB (pooled RR 3.41, 95% CI 1.81–6.45), which was higher than the risk in adults exposed to SHS (summary RR 1.32, 95% CI 1.04–1.68). Positive and significant exposure–response relationships were observed among children under 5 y (RR 5.88, 95% CI 2.09–16.54), children exposed to SHS through any parent (RR 4.20, 95% CI 1.92–9.20), and children living under the most crowded household conditions (RR 5.53, 95% CI 2.36–12.98). Associations for LTBI and active TB disease remained significant after adjustment for age, biomass fuel (BMF) use, and presence of a TB patient in the household, although the meta-analysis was limited to a subset of studies that adjusted for these variables. There was a loss of association with increased risk of LTBI (but not active TB) after adjustment for socioeconomic status (SES) and study quality. The major limitation of this analysis is the high heterogeneity in outcomes among studies of pediatric cases of LTBI and TB disease.ConclusionsWe found that SHS exposure is associated with an increase in the relative risk of LTBI and active TB after controlling for age, BMF use, and contact with a TB patient, and there was no significant association of SHS exposure with LTBI after adjustment for SES and study quality. Given the high heterogeneity among the primary studies, our analysis may not show sufficient evidence to confirm an association. In addition, considering that the TB burden is highest in countries with increasing SHS exposure, it is important to confirm these results with higher quality studies. Research in this area may have important implications for TB and tobacco control programs, especially for children in settings with high SHS exposure and TB burden.

P191 With A Low Incidence Of Drug-induced Hepatitis, Should We Be Offering Latent Tb Treatment To More Patients Over The Age Of 35?

Introduction NICE guidelines recommend patients >35 yrs at risk of tuberculosis (TB) on screening, but without active disease, should not be offered latent TB infection (LTBI) treatment unless a healthcare worker, or HIV positive. This is based on perceived risks of drug-induced hepatitis, and reduced diagnostic sensitivity of LTBI in >35’s. 3 months Rifampicin/Isoniazid (3RH) is commonly used however in a review of LTBI treatment, only one Hong-Kong based study found 1766/100,000 (n = 170) had symptomatic hepatitis or alanine aminotransferase (ALT) >250 IU (Grade 3 hepatitis). 1 Prompted by improved sensitivity of LTBI case finding with interferon gamma testing, and local case of active TB in a contact >35 yrs, we studied whether those >35 yrs with LTBI, treated with 3RH experienced greater hepatotoxicty than Method We retrospectively analysed electronic patient records detailing LTBI patient treatments from June 2008–2013 from two hospitals, collecting baseline clinical data and ALT level >2 weeks into treatment. Results Of 270 eligible patients, 151 had complete results and were included. 98/151 (65%) were 35 yrs (range 35–75), of whom 32 (60%) were male. Only 3 patients (2 males) developed ALT >250 IU/L (rate of 1,987/100,000), all patients were symptomatic and required treatment cessation. Ages were 31, 32 and 52 yrs and the single female patient was pregnant starting treatment. None required admission and all liver function returned to normal following cessation. Discussion This study, although small, provides a similar rate of hepatitis (defined >250 IU/L or symptoms) to the only previous study using the 3RH regimen and shows no age specific differences in ALT results. In light of this, we raise the question; with increasing rates of TB in the UK, a large proportion of which is attributable to latent infection, should we be offering LTBI treatment to more patients >35 yrs? This study suggests the need, and provides important information for, planning a larger study to help answer this question. Reference Ormerod et al . BTS recommendations for assessing risk and for managing Mycobacterium tuberculosis infection and disease in patients due to start anti-TNF-a Thorax 2005;60:800–805

Taima (stop) TB: the impact of a multifaceted TB awareness and door-to-door campaign in residential areas of high risk for TB in Iqaluit, Nunavut.

BackgroundThe incidence rate of active tuberculosis (TB) disease in the Canadian Territory of Nunavut has shown a rising trend over the past 10 years. In 2010 it was 60 times greater than the national incidence rate. The objective of the Taima (translates to “stop” in Inuktitut) TB study was to implement and evaluate a public health campaign to enhance existing TB prevention efforts in Nunavut.MethodsA TB awareness campaign followed by a door-to-door screening campaign was carried out in Iqaluit, Nunavut. The aim of the campaign was to raise awareness about TB, and to provide in-home screening and treatment for people living in residential areas at high risk for TB. Screening was based on geographic location rather than on individual risk factors.ResultsDuring the general awareness campaign an increase in the number of people who requested TB testing at the local public health clinic was observed. However, this increase was not sustained following cessation of the awareness campaign. Targeted TB screening in high risk residential areas in Iqaluit resulted in 224 individuals having TSTs read, and detection of 42 previously unidentified cases of latent TB, (overall yield of 18.8% or number needed to screen = 5.3). These cases of latent TB infection (LTBI) were extra cases that had not been picked up by traditional screening practices (34% relative increase within the community). This resulted in a 33% relative increase in the completion of LTBI treatment within the community. The program directly and indirectly identified 5/17 new cases of active TB disease in Iqaluit during the study period (29.5% of all incident cases).ConclusionsWhile contact tracing investigations remain a cornerstone of TB prevention, additional awareness, screening, and treatment programs like Taima TB may contribute to the successful control of TB in Aboriginal communities.

Latent TB infection in newly diagnosed lung cancer patients – A multicenter prospective observational study

ObjectivesLung cancer and tuberculosis (TB) share common risk factors and are associated with high morbidity and mortality. Coexistence of lung cancer and TB were reported in previous studies, with uncertain pathogenesis. The association between lung cancer and latent TB infection (LTBI) remains to be explored. MethodsNewly diagnosed, treatment-naïve lung cancer patients were prospectively enrolled from four referral medical centers in Taiwan. The presence of LTBI was determined by QuantiFERON-TB Gold In-Tube (QFT-GIT). Demographic characteristics and cancer-related factors associated with LTBI were investigated. The survival status was also analyzed according to the status of LTBI. ResultsA total of 340 lung cancer patients were enrolled, including 96 (28.2%) LTBI, 214 (62.9%) non-LTBI, and 30 (8.8%) QFT-GIT results-indeterminate cases. Non-adenocarcinoma cases had higher proportion of LTBI than those of adenocarcinoma, especially in patients with younger age. In multivariate analysis, COPD (OR 2.41, 95% CI 1.25–4.64), fibrocalcified lesions on chest radiogram (OR 2.73, 95% CI 1.45–5.11), and main tumor located in typical TB areas (OR 2.02, 95% CI 1.15–3.55) were independent clinical predictors for LTBI. Kaplan–Meier survival analysis demonstrated patients with indeterminate QFT-GIT results had significantly higher 1-year all-cause mortality than those with LTBI (p<0.001) and non-LTBI (p=0.003). In multivariate analysis, independent predictors for 1-year all-cause mortality included BMI<18.5 (HR 2.09, 95% CI 1.06–4.14, p=0.033), advanced stage of lung cancer (RR 7.76, 95% CI 1.90–31.78, p=0.004), and indeterminate QFT-GIT results (RR 2.40, 95% CI 1.27–4.54, p=0.007). ConclusionsMore than one-quarter of newly diagnosed lung cancer patients in Taiwan have LTBI. The independent predictors for LTBI include COPD, fibrocalcified lesions on chest radiogram, and main tumor located in typical TB areas. The survival rate is comparable between LTBI and non-LTBI cases. However, indeterminate QFT-GIT result was an independent predictor for all-cause mortality in lung cancer patients.

Serial testing using interferon-γ release assays in nursing students in India

To the Editor: We have previously shown that Indian healthcare workers have higher prevalence of latent tuberculosis infection (LTBI) and are at increased risk for new infection [1]–[4]. Interferon-γ release assays (IGRAs) have been introduced as an alternative to the tuberculin skin test (TST) for diagnosing LTBI in healthcare workers and other high-risk groups. They have logistical advantages over the TST and will not cross-react with the bacille Calmette Guerin vaccine. IGRAs are now being widely used for screening healthcare workers [5], yet recent reports indicate that switching from TST to IGRAs for the serial testing of healthcare workers may result in increased rates of test conversions and reversions [3], [6]–[8]. Most of these studies are from low tuberculosis (TB) incidence settings, with limited opportunity for nosocomial TB exposure; as a result, the increased conversion rates are considered false-positive test conversions, making it difficult for clinicians to interpret IGRA test conversions in these settings [9]. It remains unclear whether IGRA conversions are associated with TB exposure in high TB incidence settings where unprotected exposure to infectious TB patients is more common among healthcare workers. To evaluate whether IGRA conversions may represent new cases of LTBI, in a high TB incidence setting, in the absence of a gold standard for LTBI, we employed TB exposure as a proxy measure. We established a cohort of nursing students who underwent IGRA testing annually for 3 years at a tertiary level hospital in southern India [1]. Annual rates of conversions and reversions were estimated in this cohort. A relationship between occupational TB exposure and change in continuous interferon-γ (IFN-γ) levels were …

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.

Testy IGRA w Diagnostyce Zakażenia Prątkami Gruźlicy w Wybranych Sytuacjach Klinicznych

Until recently, the basic test to identify latent tuberculosis infection (LTBI) was the tuberculin skin test, despite its limitations in the form of low sensitivity and specificity. Currently, Interferon Gamma Release Assays from peripheral blood are used for a rapid diagnosis of LTBI and measurement of the interferon gamma (IFN-g) levels secreted by specific T cells stimulated with Mycobacterium tuberculosis antigens. Detection of LTBI is important in the control of people potentially at risk of TB disease, such as people remaining in close contact with BK (+) tb patient and for patients evaluated for biological treatment. The paper presents the value of IGRA in three selected clinical situations: in two cases of latent tuberculosis infection and in one case of active tuberculosis.

Role of QuantiFERON-TB-Gold In Tube assay for active and latent tuberculosis infection in investigation of tuberculosis outbreak in a university

Identification and monitoring of active tuberculosis (TB) and latent tuberculosis infection (LTBI) are the key steps to prevent transmission during a TB outbreak. The aim of this study was to evaluate the role of QuantiFERON-TB-Gold In Tube assay (QFT-GIT) in the investigation of active TB and LTBI cases during a TB outbreak in a university. In this study, enrolled students and teachers were evaluated with chest radiograph, questionnaire, and QFT-GIT test. The diagnosis of active pulmonary TB was based on sputum studies and chest radiographs. The questionnaire, which covered demographic information, underlying diseases, and environmental exposures, was applied to assess the association of risk factors by multiple logistic regressions. A total of 159 participants completed the study protocol. Positive QFT-GIT results were demonstrated in class A (75.7%; 25/33), class B (57.1%; 20/35), and class C (37.5%; 3/8) in institute 1; class D (17.3%; 8/46) in institute 2; and class E (3.1%; 1/32) in institute 3; but none among the (0/5) administrative officers, who comprised the control group. "Number of contact with active TB cases" was strongly associated and correlated with the prediction of a positive QFT-GIT result in multivariate analysis (odds ratio = 1.99; 95% confidence interval, 1.52-2.61; p < 0.0001). Seven cases progressed to active TB infection, all showing positive QFT-GIT results (100%; 7/7). Inclusion of QFT-GIT may be helpful in controlling and monitoring of active TB and LTBI cases during an investigation of a TB outbreak. The finding demonstrated that the QFT-GIT test was useful in accurately identifying infected and uninfected students, permitting rapid intervention.

Latent tuberculosis infection and associated risk factors among undergraduate healthcare students in Italy: a cross-sectional study.

BackgroundThe screening of both healthcare workers and students attending teaching hospitals for latent tuberculosis infection (LTBI) is recommended in hospitals of many countries with a low-incidence of TB, including Italy, as a fundamental tool of tuberculosis (TB) control programs. The aim of the study was to estimate the prevalence of LTBI and evaluate the main risk-factors associated with this condition in a cohort of healthcare Italian students.MethodsIn a cross-sectional study, performed between January and May 2012, 881 undergraduate students attending the Medical, Nursing, Pediatric Nursing and Midwifery Schools of the University of Genoa, trained at the IRCCS San Martino-IST Teaching Hospital of Genoa, were actively called to undergo the Tuberculin Skin Test (TST). All the TST positive cases were also tested with an Interferon-Gamma Release Assay (IGRA) to confirm the diagnosis of LTBI. A standardized questionnaire was collected for risk-assessment analysis.ResultsSeven hundred and thirty-three (83.2%) subjects underwent TST testing. The prevalence of TST positives was 1.4%, and in 4 (0.5%) out of 10 TST positive cases LTBI diagnosis was confirmed by IGRA. No difference in the prevalence of subjects who tested positive to TST emerged between pre-clinical (n = 138) and clinical (n = 595) students. No statistically significant association between TST positivity and age, gender, and BCG vaccination was observed. The main independent variable associated with TST positivity was to be born in a country with a high TB incidence (i.e., ≥20 cases per 100,000 population) (adjusted OR 102.80, 95% CI 18.09-584.04, p < 0.001).ConclusionsThe prevalence of LTBI among healthcare students resulted very low. The only significant association between TST positivity and potential risk factors was to be born in high TB incidence areas. In countries with a low incidence of TB, the screening programs of healthcare students before clinical training can be useful for the early identification and treatment of the sporadic cases of LTBI.

Prevalence of latent tuberculosis infection and its risk factors in schoolchildren and adolescents in Shanghai, China

As tuberculosis (TB) infection in childhood contributes to the pool of individuals with latent tuberculosis infection (LTBI) from which future tuberculosis cases arise, this study aimed to determine the prevalence and risk factors associated with LTBI in schoolchildren and adolescents from Shanghai, China. In this cross-sectional study, we administered T-SPOT.TB and TB infection risk factor questionnaire to children and adolescents aged between 10 and 18 years in 2010 in Shanghai. LTBI cases were defined by positive T-SPOT.TB test results and X-ray confirmation. A total of 1106 schoolchildren and adolescents were enrolled, of which 46.1% were male, and 91.8% were vaccinated with Bacille Calmette Guerin (BCG). Overall, 52 (4.7%) children had a positive T-SPOT.TB result, with significant increase in age distribution. However, none of the participants demonstrated TB-related abnormality on X-ray examination. Multivariate analysis showed that LTBI was associated with no BCG vaccination (odds ratio: 2.40; 95% confidence interval: 1.182-5.335) and a history of TB exposure (odds ratio: 6.89; 95% confidence interval: 3.095-15.35). For 46 children and adolescents with history of TB exposure, contact hours per week of TB cases were significantly associated with risk of LTBI. Prevalence of LTBI in schoolchildren and adolescents in Shanghai is relatively low compared with other high epidemic areas of TB. A higher risk of LTBI was observed among children with no BCG vaccination and those with a history of TB exposure, which suggests that the prevalence of LTBI among schoolchildren could be further reduced by strengthening BCG vaccination under the national immunization programme and enhancing contact investigation of active TB patients.

Comparison of the tuberculin skin test and Quanti-FERON-TB Gold In-Tube (QFT-G) test for the diagnosis of latent tuberculosis infection in dialysis patients

Dialysis patients are more likely than the general population to develop active tuberculosis (TB). In these patients, the availability of a highly sensitive and specific test to diagnose latent TB will ensure earlier treatment and decreased progression to active disease. In the current study, the Quanti-FERON-TB Gold In-Tube (QFT-G) test was compared with the tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection (LTBI) among 200 hemodialysis patients and 15 confirmed TB disease cases in a tertiary care center in Saudi Arabia. Among the LTBI cases, 26 (13%) were TST positive, and 65 (32.5%) were positive by the QTF-G test, with an overall agreement between the 2 tests of 75.5% (k=0.34) being observed. Among the confirmed tuberculosis disease cases, none were positive by TST, and 10 (66.7%) were positive by the QTF-G test, resulting in an overall agreement of 33.3% (k=0). A comparison between the TST and the QTF-G test was performed based on the sensitivity, specificity, and area under the curve (AUC) obtained for the tests. The QTF-G test was more sensitive and less specific than the TST in predicting the confirmed TB disease cases. When we tested the correspondence of the AUC values between the 2 diagnostic modalities, the obtained p-value was 0.0003. In conclusion, the AUCs of the examined diagnostic modalities are significantly different in predicting LTBI and tuberculosis.

The Performance of Quantiferon-TB Gold in-Tube (QFT-IT) Test Compared to Tuberculin Skin Test (TST) in Detecting Latent Tuberculosis Infection (LTBI) in the Presence of HIV Coinfection in a High TB-Burden Area with BCG-Vaccinated Population

To compare quantiferon-TB gold "in tube" (QFT-IT) with the conventional tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection (LTBI) in HIV-infected adults in a setting highly endemic for tuberculosis with BCG vaccinated population in Bangalore, Karnataka, India. The study population (100 BCG-vaccinated adults) was divided into 4 groups: HIV patients with TB patient contact, HIV patients with past history of TB, TB patients (positive control), and healthy volunteers (negative control). Overall agreement between TST and QFT-IT was 52.4% (κ = 0.22). Increasing the TST cutoff value from 5 mm to 10 mm among HIV-positive groups resulted in better agreement 62.5% in Group 1 and 81.2% in Group 2. In a setting with high TB prevalence, the TST gives increased false positives in HIV-positive groups if 5 mm is used as the cutoff value. This could be minimized by increasing the cutoff to 10 mm. The 2-step approach (initial testing of all cases with TST and confirmation of only those positive in TST by testing with QFT-IT) will be economical and help in treating LTBI cases in lower middle income countries like India.

Use of regular check-ups after completion of treatment for latent tuberculosis infection

To evaluate the efficacy of regular examination (primarily by chest radiography) following treatment for latent tuberculosis infection (LTBI), we attempted to estimate the frequency and time to onset of active tuberculosis after completion of LTBI treatment. OBJECTS & METHODS: From the Japanese national surveillance data of 2008-2011, we extracted and analyzed the number of active tuberculosis cases after the end of LTBI treatment that was registered during 2008-09. Among LTBI cases registered during 2008-09 (n = 8951), 56 active tuberculosis cases following LTBI treatment were detected by the end of 2011. Frequency of onset of active tuberculosis by the end of the second year after registration of LTBI cases were as follows: 0.57% (51/8951), all active tuberculosis cases; 0.10% (9/8951), smear-positive lung tuberculosis cases; and 0.22% (20/8951), all bacteria-positive lung tuberculosis cases. In 37 active tuberculosis cases for which the date of completion of LTBI treatment was available, 12 cases were diagnosed within 1 year and 22 within 2 years of the completion of LTBI treatment. The frequency of onset of active tuberculosis after completion of LTBI treatment was relatively low, but it did not decrease with time in the following 2 years. Hence, the validity of regular examination should be assessed, rather than specifying the duration of regular examinations after completion of LTBI treatment.

Comparison of screening strategies to improve the diagnosis of latent tuberculosis infection in the HIV-positive population: a cohort study

BackgroundHIV is the most important risk factor for progression of latent tuberculosis infection (LTBI) to active tuberculosis (TB). Detection and treatment of LTBI is necessary to reduce the increasing burden...

Latent tuberculosis infection, tuberculin skin test and vitamin D status in contacts of tuberculosis patients: a cross-sectional and case-control study

BackgroundDeficient serum vitamin D levels have been associated with incidence of tuberculosis (TB), and latent tuberculosis infection (LTBI). However, to our knowledge, no studies on vitamin D status and tuberculin skin test (TST) conversion have been published to date. The aim of this study was to estimate the associations of serum 25-hydroxyvitamin D3 (25[OH]D) status with LTBI prevalence and TST conversion in contacts of active TB in Castellon (Spain).MethodsThe study was designed in two phases: cross-sectional and case-control. From November 2009 to October 2010, contacts of 42 TB patients (36 pulmonary, and 6 extra-pulmonary) were studied in order to screen for TB. LTBI and TST conversion cases were defined following TST, clinical, analytic and radiographic examinations. Serum 25(OH)D levels were measured by electrochemiluminescence immunoassay (ECLIA) on a COBAS® 410 ROCHE® analyzer. Logistic regression models were used in the statistical analysis.ResultsThe study comprised 202 people with a participation rate of 60.1%. Only 20.3% of the participants had a sufficient serum 25(OH)D (≥ 30 ng/ml) level. In the cross-sectional phase, 50 participants had LTBI and no association between LTBI status and serum 25(OH)D was found. After 2 months, 11 out of 93 negative LTBI participants, without primary prophylaxis, presented TST conversion with initial serum 25(OH)D levels: a:19.4% (7/36): < 20 ng/ml, b:12.5% (4/32):20-29 ng/ml, and c:0%(0/25) ≥ 30 ng/ml. A sufficient serum 25(OH)D level was a protector against TST conversion a: Odds Ratio (OR) = 1.00; b: OR = 0.49 (95% confidence interval (CI) 0.07-2.66); and c: OR = 0.10 (95% CI 0.00-0.76), trends p = 0.019, adjusted for high exposure and sputum acid-fast bacilli positive index cases. The mean of serum level 25(OH)D in TST conversion cases was lower than controls,17.5 ± 5.6 ng/ml versus 25.9 ± 13.7 ng/ml (p = 0.041).ConclusionsThe results suggest that sufficient serum 25(OH)D levels protect against TST conversion.

Dépistage de l’infection tuberculeuse latente (ITL) à Paris à l’aide d’un test interféron chez des sujets contact en 2009

There are two reasons for screening contacts: one is to identify cases of secondary tuberculosis disease (TB) and the other is to identify new cases of latent tuberculosis infection (LTBI). The tuberculin skin test (TST) and the interferon-gamma-release assay (IGRA) have their limitations when used for the detection of LTBI. They neither allow a definite diagnosis of LTBI nor provide information as to the date of onset. The present study was observational, multi-centre (four centers) and retrospective. Six hundred and one contacts were included. The results of the QFT test showed 88positive (15%). Among the 144index cases, all presented with pulmonary disease and 89cases were sputum positive. In our series, 101contacts belonged to the family circle. The four factors that had a significant positive impact on the result of the QFT test were: increasing age, the region of birth of the contact (high incidence areas), both of which may indicate old infection, while contact within the family and sputum positivity of the index case probably indicate recent infection. Only sputum positivity influenced the decision to treat the LTBI. We propose a tool aimed at facilitating the decision making process in QFT positive cases. Estimation of the duration of LTBI should help the physician to decide on the need for preventative treatment as well as a search for factors that increase the risk of progression to TB disease.

Screening and follow-up of children exposed to tuberculosis cases, Luanda, Angola

This prospective study enrolled children aged < 5 years with reported contact with adult tuberculosis (TB) patients in Angola. The study sample consisted of 124 children: 70 (56.5%) were active TB cases, 22 (17.7%) had latent TB infection (LTBI) and 32 (25.8%) were TB-exposed; 14 (20%) were human immunodeficiency virus positive. After 6 months of follow-up, 31.8% of the LTBI cases had evolved to active TB and 9.4% of the non-infected children had developed active TB. The strategy of simultaneous chest X-ray and TB skin test used in this study was effective; despite this protocol, however, 31.8% LTBI children developed active TB.

Clinical applicability of Quantiferon‐TB‐Gold testing in psoriasis patients during long‐term anti‐TNF‐alpha treatment: a prospective, observational study

Psoriasis patients who are treated with tumour necrosis factor (TNF)-alpha antagonists are at increased risk of reactivation of latent tuberculosis infection (LTBI) and should be adequately screened and monitored during active treatment. To evaluate in a prospective study, the performance of Quantiferon-TB-Gold in tube (QFT) in vitro assay compared to the conventional tuberculin skin test (TST) in detecting LTBI among a cohort of non-BCG-vaccinated patients with moderate-to-severe psoriasis during long-term treatment (12 months) with TNF-alpha antagonists. A total of 50 patients underwent QFT and TST testing at baseline and after 6 and 12 months of continuous anti-TNF-alpha treatment. Diagnosis of LTBI was made on the basis of a positive QFT result and negative chest-radiographic and microbiological assays. Patients with LTBI were subjected to standard isoniazid chemoprophylaxis and after 1 month, they resumed anti-TNF-alpha treatment with subsequent QFT and TST testing after 6 months. In all the cases, a follow-up period of 12 months was observed. During the 12-month-study period, 14% of patients presented a QFT conversion. During active anti-TNF-alpha treatment, a QFT conversion was observed in 10% of patients (five cases). Agreement between QFT and TST was moderate (κ=0.408) at screening, good (κ=0.734) after 6 months and fair (κ=0.328) after 12 months of treatment. A total of 18% of patients presented a positive, discordant TST during the study period. A single-test QFT-based screening strategy for LTBI in psoriasis patients receiving long-term anti-TNF-alpha treatment could reduce the incidence of false-positive LTBI cases, preventing unnecessary TB chemoprophylaxis.

S5 Prevalence of latent tuberculosis infection in immigrants to the UK: findings from a multi-centre study

<h3>Background</h3> Notifications for tuberculosis (TB) in the United Kingdom (UK) increased by 30% between 1992 and 2007 with overseas-born migrants accounting for 72% of cases in 2007. Much of this increase is due to the synergy of migration from high-TB burden countries and the reactivation of pre-existing latent TB infection (LTBI). Since 2006, NICE guidance advocates screening for LTBI in all children from countries with a TB incidence &gt;40/100 000 and adults from Sub-Saharan Africa and countries with a TB incidence &gt;500/100 000. The rationale underpinning these guidelines remains unclear particularly as there are little data on the prevalence of LTBI in immigrants to the UK from regions with different TB incidence rates. <h3>Aims</h3> To quantify the prevalence of LTBI in immigrants, assess factors associated with IGRA positivity and to determine LTBI yield from current screening thresholds recommended by NICE. <h3>Methods</h3> Analysis of data prospectively obtained through IGRA testing (QuantiFERON-Gold/QuantiFERON-Gold-in-tube) of immigrants in three different centres in the UK during 2008–2010. Descriptive analyses were undertaken. Yields at different screening thresholds were calculated. Subsequent univariate and multivariate analyses were undertaken to assess independent factors associated with IGRA positivity; p&lt;0.05 considered significant. <h3>Results</h3> In total 915 immigrants were screened during the study period. Median age was 26.8 years (interquartile range 22–33), 50.6% were female and 72.5% had previously been BCG vaccinated. 48.9% and 28.5% of migrants screened originated from the Indian Subcontinent and Sub-Saharan Africa, respectively. Overall 911/915 individuals had determinate IGRA results—199 (21.7%) tested positive and 712 (77.8%) tested negative; 4 (0.4%) individuals had indeterminate results. Multivariate analysis revealed that increasing age (p&lt;0.0001) and increasing TB incidence of country of origin (p=0.0014) were independently associated with IGRA positivity. Applying current NICE guidance resulted in a yield of 76/311 (24.4%) but would miss 61.8% of the immigrant population with LTBI (Abstract S5 Table 1). <h3>Conclusions</h3> Immigrants have a high prevalence of LTBI but current NICE guidance detects only 38.2% of new entrants with LTBI. Given the high rates of reactivation of LTBI in new entrants, our findings suggest that consideration should be given to reducing the screening threshold to include those from the Indian Subcontinent (incidence 170/100 000) which would result in 67.8% of all LTBI cases being identified.

Evaluation of identifying tuberculosis infection and disease in a rural institutionalized population

Context Although the overall prevalence of tuberculosis (TB) in the United States is declining, correctional facilities continue to encounter a higher prevalence of this disease. Despite mandatory reporting laws for active TB, data for latent TB infection (LTBI) remains sketchy because reporting it is not required. Purpose Investigation of the period prevalence of LTBI in a rural Ohio regional jail compared with other populations in the region to determine the need and adequacy of the screening program. Methods Data collected on inmates was compared with data collected on hospital employees within the same geographic region. Findings Between January 2006 and July 2007, staff at the jail tested 1274 inmates for TB using the Mantoux purified protein derivative (PPD) method. Ten inmates (6 in 2006 and 4 in 2007) tested positive. All 10 cases were followed with a negative chest radiograph, leading to the diagnosis of LTBI. The overall incidence for the jail for LTBI was 0.8%, with 0% active cases. However, 85 inmates (6.7% of the population) were released before a PPD interpretation could be completed. In the comparative population, 651 hospital employees were tested for TB. Of these, 32 employees tested positive (LTBI prevalence of 4.9%). There were no cases of active TB reported. Conclusion The prevalence of LTBI in a rural jail (0.8%) is lower than the comparative sample population at a local hospital (4.9%). The rapid release of inmates (6.7%) indicates that TB data is incomplete and that potential cases of LTBI could have been unreported because of missed opportunity for interpretation of skin tests.