Effect of bacille Calmette-Guérin vaccination on tuberculin reactivity

Safety and Immunogenicity of the ID93 + GLA-SE Tuberculosis Vaccine in BCG-Vaccinated Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Phase 2 Trial

INTRODUCTION

This randomized, double-blind, placebo-controlled, phase 2a trial was conducted to evaluate the safety and immunogenicity of the ID93 + glucopyranosyl lipid adjuvant (GLA)-stable emulsion (SE) vaccine in human immunodeficiency virus (HIV)-negative, previously Bacillus Calmette-Guérin (BCG)-vaccinated, and QuantiFERON-TB-negative healthy adults in South Korea.

METHODS

Adults (n = 107) with no signs or symptoms of tuberculosis were randomly assigned to receive three intramuscular injections of 2 μg ID93 + 5 μg GLA-SE, 10 μg ID93 + 5 μg GLA-SE, or 0.9% normal saline placebo on days 0, 28, and 56. For safety assessment, data on solicited adverse events (AEs), unsolicited AEs, serious AEs (SAEs), and special interest AEs were collected. Antigen-specific antibody responses were measured using serum enzyme-linked immunosorbent assay. T-cell immune responses were measured using enzyme-linked immunospot and intracellular cytokine staining.

RESULTS

No SAEs, deaths, or AEs leading to treatment discontinuation were found. The solicited local and systemic AEs observed were consistent with those previously reported. Compared with adults administered with the placebo, those administered with three intramuscular vaccine injections exhibited significantly higher antigen-specific antibody levels and Type 1 T-helper cellular immune responses.

CONCLUSION

The ID93 + GLA-SE vaccine induced antigen-specific cellular and humoral immune responses, with an acceptable safety profile in previously healthy, BCG-vaccinated, Mycobacterium tuberculosis-uninfected adult healthcare workers.

TRIAL REGISTRATION

This clinical trial was retrospectively registered on 16 January 2019 at Clinicaltrials.gov (NCT03806686).

Implementation of a Routine Screening Program for Latent Tuberculosis Infection among Patients with Acute Leukemia at a Canadian Cancer Center

BACKGROUND

Screening for latent tuberculosis infection (LTBI) in patients with hematological malignancy is recommended because of their increased risk of tuberculosis (TB). We assessed the utility of tuberculin skin test (TST) screening in patients with acute leukemia and subsequent outcomes of LTBI treatment.

METHODS

We retrospectively evaluated patients ≥16 years of age with acute leukemia from 2013-2014 with a TST planted and read prior to the initiation of antineoplastic chemotherapy treatment. Demographics, clinical information and treatment outcomes of LTBI therapy were compared between patients with positive TST (≥10 mm induration) and negative TST.

RESULTS

A total of 389 patients with acute leukemia were included in the cohort. Of them, 37/389 (9.5%) had a positive TST. Only 3.4% (8/235) of individuals originating from North and South America as well as the Caribbean were TST positive, while 21% (20/95) of individuals from Asia were TST positive. Diagnostic imaging findings consistent with prior tuberculosis infection were higher in TST positive patients compared to TST negative ones (29.7% versus 9.4%, p < 0.0001). Furthermore, 31/38 patients (81.6%) who were TST positive received LTBI therapy, which was well tolerated. There was no significant difference in overall survival among those who received LTBI therapy compared to those who did not. No patients developed active TB.

CONCLUSIONS

Universal screening with TST may be of low yield in individuals with acute leukemia unless patients originate from a TB endemic country. When therapy for LTBI is prescribed, patients with acute leukemia do not experience drug-induced liver toxicity and are likely to complete the intended duration of therapy, thus preventing the development of active tuberculosis.

Determination of tuberculosis-related volatile organic biomarker methyl nicotinate in vapor using fluorescent assay based on quantum dots and cobalt-containing porphyrin nanosheets

Methyl nicotinate (MN) is a representative and typical volatile organic marker of Mycobacterium tuberculosis, and the specific detection of MN in human breath facilitates non-invasive, rapid, and accurate epidemic screening of tuberculosis infection. Herein, we constructed a fluorescent assay consisted of CdTe quantum dots (QD) and cobalt-metalized tetrakis(4-carboxyphenyl) porphyrin (CoTCPP) nanosheets to determine methyl nicotinate (MN) in vapor samples. Red-emission QD (λ_ex=370 nm, λ_em=658 nm) acts as signal switches whose fluorescence signals can be effectively quenched by CoTCPP nanosheets but restored in the presence of MN. The strategy relied on the distinct binding affinity of cobalt ion and MN. MN restored the fluorescence of QD quenched by CoTCPP in a concentration-dependent manner, which exhibited a well-linear relationship in the range 1-100 μM, and a limit of detection of 0.59 μM. The proposed platform showed sensitivity and selectivity to detect MN in vapor samples with satisfactory RSD below 3.33%. The method is cheap, simple, and relatively rapid (detected within 4 min), which suggests a potential in tuberculosis diagnosis in resource- and professional-lacked areas.

Sensitivity, specificity, and safety of a novel ESAT6-CFP10 skin test for tuberculosis infection in China: two randomized, self-controlled, parallel-group phase 2b trials

BACKGROUND

Diagnostics to identify tuberculosis infection are limited. We aimed to assess the diagnostic accuracy and safety of the novel ESAT6-CFP10 (EC) skin test for tuberculosis infection in Chinese adults.

METHODS

We conducted two randomized, parallel-group clinical trials in healthy participants and tuberculosis patients. All participants were tested with the T-SPOT.TB test, then received EC skin test and tuberculin skin test (TST). The diameter of skin indurations and/or redness at injection sites were measured at different time periods. A Bacillus Calmette Guerin (BCG) model was also established to assess the diagnosis of tuberculosis infection using EC skin test.

RESULTS

In total, 777 healthy participants and 96 tuberculosis patients were allocated to receive the EC skin test at 1.0μg/0.1ml or 0.5μg/0.1ml. The area under the curve was 0.95 (95% CI, 0.91-0.97) from the EC skin test at a dose of 1.0μg/0.1ml at 24-72 hours. Compared to the T-SPOT.TB test, the EC skin test demonstrated similar sensitivity (87.5, 95% CI 77.8-97.2 versus 86.5, 95% CI 79.5-93.4) and specificity (98.9, 95% CI 96.0-99.9 versus 96.1, 95% CI 93.5-97.8). Among BCG vaccinated participants, the EC skin test had high consistency with the T-SPOT.TB test (96.3, 95% CI, 92.0-100.0). No serious adverse events related to the EC skin test were observed.

CONCLUSIONS

The EC skin test demonstrated both high specificity and sensitivity at a dose of 1.0μg/0.1ml, comparable to the T-SPOT.TB test. The diagnostic accuracy of the EC skin test was not impacted by BCG vaccination.

Specificity of tuberculin skin test improved by BCG immunization schedule change in Japan

INTRODUCTION

Tuberculin skin test (TST) has been used to diagnose tuberculosis (TB) and latent tuberculosis infection (LTBI). However, in Bacillus Calmette-Guérin (BCG) vaccinated patients, TST tends to produce false-positive results. According to the previous vaccination schedule, Japanese people were mandated to receive up to three doses of BCG-vaccine. The vaccination schedule was changed in 2003 and as per the new schedule, only infants are administered a dose of BCG vaccine. Our hypothesis is that this change can lead to a reduction in the cross-reaction to TST.

METHODS

We evaluated the TST results obtained from 1097 recruits from six defense camps and 667 recruits from an air base. These TST data were divided into two groups according to the date of birth: a new group and an old group according to the BCG immunization schedule. We then analyzed positive and negative reaction of TST and erythema sizes.

RESULTS

We confirmed that the change in BCG-vaccination schedule significantly decreased TST false-positive reaction (P_meta = 1.4 × 10^-18; risk ratio = 0.83; 95% confidence interval: 0.80-0.87) and erythema size (P_meta = 1.1 × 10^-4; mean difference = 6.6 mm; 95% confidence interval: 3.2 mm-9.9 mm).

CONCLUSIONS

We showed the reduction in BCG cross-reaction to TST, in the new BCG vaccination schedule group, compared to the old group, we also have extracted information on the improvement in the specificity of TST for LTBI and TB diagnosis, which resulted from BCG schedule change.

Is latent tuberculosis infection challenging in Iranian health care workers? A systematic review and meta-analysis

Background

The high chances of getting latent tuberculosis infection (LTBI) among health care workers (HCWs) will an enormous problem in low and upper-middle-income countries.

Method

Search strategies were done through both national and international databases include SID, Barakat knowledge network system, Irandoc, Magiran, Iranian national library, web of science, Scopus, PubMed/MEDLINE, OVID, EMBASE, the Cochrane library, and Google Scholar search engine. The Persian and the English languages were used as the filter in national and international databases, respectively. Medical Subject Headings (MeSH) terms was used to controlling comprehensive vocabulary. The search terms were conducted without time limitation till January 01, 2019.

Results

The prevalence of LTBI in Iranian’s HCWs, based on the PPD test was 27.13% [CI95%: 18.64–37.7]. The highest prevalence of LTBI in Iranian’s HCWs were estimated 41.4% [CI95%: 25.4–59.5] in the north, and 33.8% [CI95%: 21.1–49.3] in the west. The lowest prevalence of LTBI was evaluated 18.2% [CI95%: 3.4–58.2] in the south of Iran. The prevalence of LTBI in Iranian’s HCWs who had work-experience more than 20 years old were estimated 20.49% [CI95%: 11–34.97]. In the PPD test, the prevalence of LTBI in Iranian’s HCWs who had received the Bacille Calmette–Guérin (BCG) was estimated 15% [CI95%: 3.6–47.73]. While, in the QFT, the prevalence of LTBI in Iranian’s HCWs in non-vaccinated was estimated 25.71% [CI95%: 13.96–42.49].

Conclusions

This meta-analysis shows the highest prevalence of LTBI in Iranian’s HCWs in the north and the west probably due to neighboring countries like Azerbaijan and Iraq, respectively. It seems that Iranian’s HCWs have not received the necessary training to prevent of TB. We also found that BCG was not able to protect Iranian’s HCWs from TB infections, completely.

Trends in Diagnosis for Active Tuberculosis Using Nanomaterials

Background:

Tuberculosis (TB), one of the leading causes of death worldwide, is difficult to diagnose based only on signs and symptoms. Methods for TB detection are continuously being researched to design novel effective clinical tools for the diagnosis of TB.

Objective:

This article reviews the methods to diagnose TB at the latent and active stages and to recognize prospective TB diagnostic methods based on nanomaterials.

Methods:

The current methods for TB diagnosis were reviewed by evaluating their advantages and disadvantages. Furthermore, the trends in TB detection using nanomaterials were discussed regarding their performance capacity for clinical diagnostic applications.

Results:

Current methods such as microscopy, culture, and tuberculin skin test are still being employed to diagnose TB, however, a highly sensitive point of care tool without false results is still needed. The utilization of nanomaterials to detect the specific TB biomarkers with high sensitivity and specificity can provide a possible strategy to rapidly diagnose TB. Although it is challenging for nanodiagnostic platforms to be assessed in clinical trials, active TB diagnosis using nanomaterials is highly expected to achieve clinical significance for regular application. In addition, aspects and future directions in developing the high-efficiency tools to diagnose active TB using advanced nanomaterials are expounded.

Conclusion:

This review suggests that nanomaterials have high potential as rapid, costeffective tools to enhance the diagnostic sensitivity and specificity for the accurate diagnosis, treatment, and prevention of TB. Hence, portable nanobiosensors can be alternative effective tests to be exploited globally after clinical trial execution.

Prevalence of and risk factors associated with latent tuberculosis in Singapore: A cross-sectional survey

OBJECTIVES

This first cross-sectional survey on latent tuberculosis infection (LTBI) in Singapore was performed by utilizing the QuantiFERON Gold In-tube (QFT-GIT) assay to collect data on the prevalence of LTBI and to identify potential risk factors associated with LTBI.

METHODS

Nationwide household addresses were selected randomly for enumeration, and Singaporeans or Permanent Residents aged 18-79 years were identified. One eligible member per household was selected using the Kish grid. Each participant answered a questionnaire assessing their medical history (including tuberculosis (TB)), socio-economic factors, and lifestyle factors. They also provided a blood specimen for the QFT-GIT assay. Participants with a positive QFT-GIT result were defined as having LTBI if they were asymptomatic. To identify independent risk factors, adjusted hazard ratios were obtained using the multivariable modified Breslow-Cox proportional hazards model.

RESULTS

An overall QFT-GIT positivity rate of 12.7% was detected amongst 1682 Singapore residents. There was a wide variation in the positivity rate according to the participants' country of birth. Higher LTBI prevalence was also significantly associated with increasing age, lower educational and socio-economic status, and alcohol use.

CONCLUSIONS

Given the high prevalence of LTBI amongst foreign-born residents from regional countries, similar studies should be conducted amongst migrants in Singapore to improve national guidelines on screening and preventive treatment against LTBI.

Screening of latent tuberculosis infection among health care workers working in Hajj pilgrimage area in Saudi Arabia, using interferon gamma release assay and tuberculin skin test

BACKGROUND

Interferon gamma release assays (IGRA) is highly specific for Mycobacterium tuberculosis and is the preferred test in BCG-vaccinated individuals. The few studies that have screened health care workers (HCWs) in Saudi Arabia for latent tuberculosis infection (LTBI) using IGRA have varied in agreement with the traditional tuberculin skin test (TST).

OBJECTIVE

Assess the prevalence of LTBI among HCWs working in the Hajj pilgrimage using IGRA and TST and measuring their agreement.

DESIGN

Cross-sectional prospective.

SETTING

Multiple non-tertiary care hospitals.

PATIENTS AND METHODS

HCWs who worked during the Hajj pilgrimage in Saudi Arabia in December 2015. Data was collected by standarized questionnaire. Samples were drawn and analyzed by standard methods.

MAIN OUTCOME MEASURES

The prevalence of LTBI among HCW and the agreement by kappa statistic between QFT-GIT and TST.

SAMPLE SIZE

520 subjects.

RESULTS

Nurses accounted for 30.7% of the sample and physicians, 19.2%. The majority were BCG vaccinated (98.5%). There were a total of 56 positive by QFT-GIT and the LTBI rate was 10.8%. In 50 QFT positive/476 TST negative the LTBI rate was 10.5% in discordant tests, and in 6 QFT positive/44 TST positive it was 13.6% in concordant tests. The overall agreement between both tests was poor-83% and kappa was 0.02. LTBI prevalence was associated with longer employment (13.1 [9.2] years). The QFT-GIT positive test was significantly higher in physicians (P=.02) and in HCWs working in chest hospitals 16/76 (21.05%) (P=.001).

CONCLUSION

Agreement between the tests was poor. QFT-GIT detected LTBI when TST was negative in HCWs who had a history of close contact with TB patients.

LIMITATIONS

A second step TST was not feasible within 2-3 weeks.

CONFLICT OF INTEREST

None.

Association Between Bacillus Calmette-Guérin Vaccination and Childhood Asthma in the Quebec Birth Cohort on Immunity and Health

We estimated the association between bacillus Calmette-Guérin (BCG) vaccination and childhood asthma in a birth cohort using administrative databases, and we determined the impact of adjusting for potential confounders collected from a subset of the cohort members. Data were collected in 2 waves: 1) Administrative data for 76,623 individuals (stage 1) was gathered from the Quebec Birth Cohort on Immunity and Health (1974-1994), including BCG vaccination status, perinatal and sociodemographic characteristics, and use of health services for asthma; and 2) self-reported asthma risk factors were collected in 2012 by telephone interviews with 1,643 participants (stage 2) using a balanced 2-stage sampling design. We estimated odds ratios and 95% confidence intervals for asthma using logistic regression and correcting for the known sampling fractions from stage 1 to stage 2, overall and sex-stratified. In total, 35,612 (46.5%) individuals were BCG vaccinated, and 5,870 (7.7%) had asthma. The final odds ratio, integrating results from both stages of sampling, was 0.95 (95% confidence interval: 0.87, 1.04). Results did not differ according to sex (P for interaction = 0.327). To our knowledge, this is the largest study ever conducted on this topic, and using the best possible comprehensive adjustment for confounders, we found no association between BCG vaccination and asthma.

Bacillus Calmette-Guérin (BCG) vaccination patterns in the province of Québec, Canada, 1956-1974

BACKGROUND

In the province of Québec, Canada, the Bacillus Calmette-Guérin (BCG) vaccine was offered to newborns and school-age children from the 1950s to mid-1970s in an organized tuberculosis prevention program.

OBJECTIVE

We aimed to describe the annual rates of skin test administration, proportion of skin tests that were positive, and rates of BCG vaccination from 1956 to 1974 according to age, sex, and administrative region.

METHODS

For rates, numerators were extracted from the Québec BCG Vaccination Registry whereas population denominators were obtained from the Canadian Census and governmental publications. Time trends were assessed with linear regression.

RESULTS

A total of 2,755,336 skin tests and 2,531,366 BCG vaccinations were administered. Yearly rates of skin tests, routinely administered before vaccination among all except newborns, were highest among children aged 5-9 (9.3 per 100) and 10-14years (7.9 per 100). The proportion of positive skin tests varied greatly by age, ranging from 10.2% among children <1year to 67.2% among adults ≥20years. The vast majority of individuals who had a negative skin test were subsequently vaccinated, whereas those with a positive result were not, as per recommended guidelines. The average annual vaccination rate was highest among children aged <1year (43.8 per 100) and 5-9year-olds (6.9 per 100). There were salient differences in immunization rates, including positive skin tests and vaccinations, across administrative regions but no difference by sex.

CONCLUSION

This is the first comprehensive description of the tuberculosis prevention program in Québec which offered free, non-mandatory BCG vaccination. Our results confirm that the targeted groups, newborns and school-age children, were preferentially reached. Socioeconomic, demographic, and organizational factors may explain regional differences in immunization rates. Beyond presenting a historical context for this vaccination campaign, our findings are relevant to contemporary uses of the Québec BCG Vaccination Registry in epidemiological research.

Diagnosis of Latent Tuberculosis Infection

For 2015, tuberculosis (TB) incidence in the United States has plateaued at 3.0 per 100,000. This remains the lowest case rate since recording started. On the global level, although the TB epidemic is larger than previously estimated, TB deaths and incidence rate continue to fall. For both low and high incidence countries, accelerating the decline in TB incidence towards elimination goals requires that more emphasis be placed on strengthening systems for detection and treatment of latent TB infection (LTBI) in addition to improving TB care globally. Here, we review the tuberculin skin test and gamma interferon release assays currently available for the detection of LTBI.

The Long-term Effect of Bacille Calmette-Guérin Vaccination on Tuberculin Skin Testing: A 55-Year Follow-Up Study

BACKGROUND

Bacille Calmette-Guérin (BCG) vaccination is known to cause false-positive tuberculin skin test (TST) results from cross-reactions with mycobacterial antigens. However, the duration of BCG vaccination influence on the TST is poorly characterized. The objective of this study was to assess the long-term effect of BCG vaccination on TST reactivity.

METHODS

Data on TST reactivity were prospectively collected during 1935 to 1947 as part of a clinical trial among Native Americans/Alaskan Natives and were retrospectively collected thereafter between 1948 and 1998. TST induration of ≥ 10 mm was defined as a positive reaction. Kaplan-Meier analysis and multivariate Cox regression were used to compare the time to TST conversion and reversion between the BCG and placebo groups.

RESULTS

BCG vaccination after infancy was associated with an increased risk of TST reactivity in the first 15 years after vaccination (adjusted hazard ratio [HR], 2.33). This association remained during the interval 16 to 55 years after vaccination, although the effect was attenuated (adjusted HR, 1.26). Age at vaccination modestly impacted the effect of BCG on TST results in the first 15 years. Positive TST results among the BCG-vaccinated group were more likely to revert to negative results during the first 15 years but not in the latter period.

CONCLUSIONS

This study provides evidence that BCG vaccination after infancy may influence TST results beyond the 10-year period conventionally accepted by the Centers for Disease Control and Prevention (CDC), extending up to 55 years after vaccination. This suggests that BCG vaccination should be taken into account when interpreting TST results regardless of the time elapsed since vaccination.

The specialist physician's approach to rheumatoid arthritis in South Africa

Rheumatoid arthritis (RA) is expected to increase in Africa and South Africa. Due to the low numbers of rheumatologists in South Africa, specialist physicians also have to care for patients with RA. Furthermore several new developments have taken place in recent years which improved the management and outcome of RA. Classification criteria were updated, assessment follow-up tools were refined and above all, several new biological disease-modifying anti-rheumatic drugs were developed. Therefore it is imperative for specialist physicians to update themselves with the newest developments in the management of RA. This article provides an overview of the newest developments in the management of RA in the South African context. This approach may well apply to countries with similar specialist to patient ratios and disease profiles.

Tuberculin skin test positivity without tuberculosis contact: A major challenge in childhood

AIM

Worldwide, tuberculin skin tests (TSTs) commonly give false positive results for those who had been given the Bacillus-Calmette-Guerin vaccine such as is routinely administered in Turkey. This study aimed to evaluate the patients referred to us who had positive TSTs despite lack of tuberculosis (TB) disease contacts.

METHODS

Between September 2011 and September 2012, 183 patients were prospectively evaluated for differential diagnosis of TST positivity despite lack of TB disease contact. They were then followed up by us to determine an accurate diagnosis.

RESULTS

Among our patients' most common symptoms indicating a need for TST were chronic cough, productive cough or sputum expectoration, and recurrent or persistent wheezing. Chest x-rays were taken of all patients, and the findings were noted. Interferon gamma release assays were performed on 75% of the patients, of which 96% were negative for TB. The most common final diagnoses were asthma (44%), allergic rhinitis (13%), bronchopneumonia (11%) and reactive lymphadenitis (6.5%). Further evaluations for TB were required of 36 patients, and TB disease was established in 12 of them (6.5%).

CONCLUSIONS

In patients who had had no known TB contact, the most common symptom indicating need for TST was chronic cough; the most common diagnoses were asthma and allergic rhinitis. Cavitary lesions, haemoptysis, persistent infiltration, pleural effusion and thoracic lymphadenopathy despite antibiotherapy should alert physicians to the possibility of TB.

Epidemiology and clinical management of tuberculosis in children in Canada

Although often regarded as a foreign disease, latent tuberculosis or tuberculosis disease will be encountered in many clinical situations by the Canadian child health practitioner. There are key differences between tuberculosis in children and adults. In the present article, the changing epidemiology of tuberculosis in children in Canada and around the world, the pathogenesis of infection, diagnostic tests, and clinical management of childhood latent tuberculosis and tuberculosis disease are reviewed.

T-Spot.TB outperforms tuberculin skin test in predicting development of active tuberculosis among household contacts

BACKGROUND AND OBJECTIVE

In Hong Kong, neonatal Bacillus Calmette-Guerin (BCG) vaccination is practiced with 99% coverage. This study was to compare the performance of T-Spot.TB and tuberculin skin test (TST) in predicting tuberculosis (TB) among household contacts.

METHODS

From 1 March 2006 to 31 July 2010, 1049 asymptomatic household contacts of smear-positive patients were simultaneously tested with T-Spot.TB and TST, and then followed for up to 5 years for development of TB. Attending clinicians and subjects were blinded to the results of T-Spot.TB.

RESULTS

T-Spot.TB gave a significantly higher positive rate (32.7% vs 22.1%) and better association with exposure time than TST at the 15 mm cut-off. Agreement between T-Spot.TB and TST using cut-offs of 5, 10 and 15 mm were relatively poor (kappa 0.25-0.41) irrespective of presence or absence of BCG scar. Only T-Spot.TB positivity was negatively associated with BCG scar. Both T-Spot.TB (incidence rate ratio between test-positive and test-negative subjects, IRR: 8.2) and TST (IRR: 4.1, 6.1 and 2.8, using cut-offs of 5 mm, 10 mm and 15 mm, respectively) helped to predict TB. Using a TST cut-off of 15 mm, 56% of future TB cases and 62.5% of bacteriologically confirmed cases were missed. Lowering the TST cut-off to 10 mm or 5 mm could achieve sensitivity comparable with that of T-Spot.TB, but at the expense of lower specificities, with more positive tests (thus requiring treatment) per case of TB predicted.

CONCLUSIONS

T-Spot.TB outperformed TST in predicting TB among household contacts in a high-income area with widespread BCG vaccination coverage.

Effect of isoniazid on antigen-specific interferon-γ secretion in latent tuberculosis

Treatment of persons with latent tuberculosis (TB) infection at greatest risk of reactivation is an important component of TB control and elimination strategies. Biomarkers evaluating the effectiveness of treatment of latent TB infection have not yet been identified. This information would enhance control efforts and assist the evaluation of new treatment regimes.

We designed a two-group, two-arm, randomised clinical study of tuberculin skin test-positive participants: 26 with documented contact with TB patients and 34 with non-documented contact. Participants in each group were randomly assigned to the immediate- or deferred-isoniazid treatment arms. Assays of in vitro interferon (IFN)-γ secretion in response to recombinant Rv1737 and overlapping synthetic peptide pools from various groups of immunodominant proteins were performed.

During isoniazid therapy, a significant increase from baseline in the proportion of IFN-γ responders to the 10-kDa culture filtrate protein, Rv2031, Rv0849, Rv1986, Rv2659c, Rv2693c and the recombinant Rv1737 protein was observed (p⩽0.05). The peptide pool of Rv0849 and Rv1737 recombinant proteins induced the highest percentage of IFN-γ responders after isoniazid therapy.

The in vitro IFN-γ responses to these proteins might represent useful markers to evaluate changes associated with treatment of latent TB infection.

Peptide pool of Rv0849 and recombinant protein Rv1737 may be useful to test the efficacy of treatment of latentTBhttp://ow.ly/Catld

Prevalence of tuberculosis symptoms and latent tuberculous infection among prisoners in northeastern Malaysia

SETTING

There are currently no routine screening procedures for active tuberculosis (TB) or latent tuberculous infection (LTBI) in Malaysian prisons.

OBJECTIVE

To determine the prevalence and correlates of LTBI and active TB symptoms among Malaysian prisoners with and without human immunodeficiency virus (HIV) infection using the tuberculin skin test (TST) and the World Health Organization TB symptom-based screening instrument.

DESIGN

A cross-sectional survey of 266 prisoners was performed in Kelantan, Malaysia. Consenting participants underwent two-step TST and were screened for active TB symptoms. Standardized cut-offs of respectively ≥5 and ≥10 mm were used to define reactive TST among prisoners with and without HIV. Clinical and behavioral data were assessed and HIV-infected prisoners were stratified by CD4 status.

RESULTS

Overall LTBI prevalence was 87.6%, with significantly lower TST reactivity among HIV-infected than non-HIV-infected prisoners (83.6% vs. 91.5%, P < 0.05); however, TB symptoms were similar (16.9% vs. 10.1%, P = 0.105). On multivariate analysis, previous incarceration (aOR 4.61, 95%CI 1.76-12.1) was the only significant correlate of LTBI. Increasing age (aOR 1.07, 95%CI 1.01-1.13), lower body mass index (aOR 0.82, 95%CI 0.70-0.96) and TST-reactive status (aOR 3.46, 95%CI 1.20-9.97) were correlated with TB symptoms.

CONCLUSION

LTBI is highly prevalent, associated with previous incarceration, and suggests the need for routine TB screening on entry to Malaysian prisons.

Evaluation of three immunological tests for the diagnosis of pulmonary tuberculosis in a rural endemic area of Bangladesh

OBJECTIVE

Bangladesh is a high tuberculosis burden country. It is always challenging to diagnose active pulmonary tuberculosis (PTB) cases in rural areas where the setting up of conventional microscopic and cultural diagnostic tools is difficult. The objective of the present study is to find a feasible, reliable and easily accessible alternative diagnostic approach for PTB in the rural areas of Bangladesh.

METHODS

A total of 86 sputum samples were collected from clinically suspected PTB patients of Anantapur village, an underdeveloped remote area of Netrokona district, Bangladesh. Sputum samples were screened by Ziehl-Neelsen (Z-N) and fluorescence staining methods and were categorized as smear-positive active PTB cases (n=50) and smear-negative controls (n=36); then the performance of three popular immunological tests were evaluated, including ICT, ELISA and Mantoux tests (MT).

RESULTS

The sensitivity of ICT, ELISA, and MT (10mm induration size) was 68%, 84% and 96%, respectively, and the specificity of these tests was 94.4%, 80.6% and 52.8%, respectively. When the cut-off size of induration in MT was changed from 10 to ⩾15mm, the sensitivity and specificity of MT became 92% and 83.3%, respectively. It was also found that the interpretation of MT was not significantly affected by BCG vaccination when ⩾15mm induration was taken as a cut-off value.

CONCLUSION

Considering the resource-constraints of rural and remote areas, the Mantoux test could be an alternative tool for the diagnosis of active PTB.

Tuberculin test can be read after 24 hours in adolescent children

OBJECTIVE

To assess readability of 24-h tuberculin response in adolescent school children.

DESIGN

Prospective observational study in school.

SUBJECTS

601 healthy adolescent children.

INTERVENTIONS

Tuberculin (1TU PPD RT23 Tween80) was administered and indurations at 24 and 72 h were compared.

MAIN OUTCOME MEASURE

Tuberculin reaction at 24 h.

RESULTS

One hundred twelve children (18.6%) had a positive tuberculin reaction. Prevalence of tuberculin positivity was least (14.2%) in the 10-year age-group and maximum in the 13-year age-group (21.2%). When individual values of tuberculin reaction at 24 and 72 h were compared, a significant difference was noted irrespective of the tuberculin status (t = 8.46, p = 0.001). However, when tuberculin reaction was considered as positive or negative, this difference was not significant (t = 1.89, p > 0.05).

CONCLUSIONS

Tuberculin status in adolescents can be read as positive or negative at 24 h, irrespective of their bacillus Calmette-Guérin scar status.

The Québec BCG Vaccination Registry (1956-1992): assessing data quality and linkage with administrative health databases

Background

Vaccination registries have undoubtedly proven useful for estimating vaccination coverage as well as examining vaccine safety and effectiveness. However, their use for population health research is often limited. The Bacillus Calmette-Guérin (BCG) Vaccination Registry for the Canadian province of Québec comprises some 4 million vaccination records (1926-1992). This registry represents a unique opportunity to study potential associations between BCG vaccination and various health outcomes. So far, such studies have been hampered by the absence of a computerized version of the registry. We determined the completeness and accuracy of the recently computerized BCG Vaccination Registry, as well as examined its linkability with demographic and administrative medical databases.

Methods

Two systematically selected verification samples, each representing ~0.1% of the registry, were used to ascertain accuracy and completeness of the electronic BCG Vaccination Registry. Agreement between the paper [listings (n = 4,987 records) and vaccination certificates (n = 4,709 records)] and electronic formats was determined along several nominal and BCG-related variables. Linkage feasibility with the Birth Registry (probabilistic approach) and provincial Healthcare Registration File (deterministic approach) was examined using nominal identifiers for a random sample of 3,500 individuals born from 1961 to 1974 and BCG vaccinated between 1970 and 1974.

Results

Exact agreement was observed for 99.6% and 81.5% of records upon comparing, respectively, the paper listings and vaccination certificates to their corresponding computerized records. The proportion of successful linkage was 77% with the Birth Registry, 70% with the Healthcare Registration File, 57% with both, and varied by birth year.

Conclusions

Computerization of this Registry yielded excellent results. The registry was complete and accurate, and linkage with administrative databases was highly feasible. This study represents the first step towards assembling large scale population-based epidemiological studies which will enable filling important knowledge gaps on the potential health effects of early life non-specific stimulation of the immune function, as resulting from BCG vaccination.

Potential association of pulmonary tuberculosis with genetic polymorphisms of toll-like receptor 9 and interferon-gamma in a Chinese population

Background

Association studies have been employed to investigate the relationships between host single nucleotide polymorphisms (SNPs) and susceptibility to pulmonary Tuberculosis (PTB). However, such candidate genetic markers have not been widely studied in Chinese population, especially with respect to the disease development from latent M. tuberculosis infection (LTBI).

Methods

In this case–control study, 44 candidate SNPs were examined in a total of 600 participants (PTB patients, LTBI controls and healthy controls without M. tuberculosis infection) from Zhengzhou, China. The two groups of controls were frequency matched on gender and age with PTB patients. Genotyping was carried out by the Illumina Golden Gate assay.

Results

When comparing PTB patients with LTBI controls but not healthy controls without M. tuberculosis infection, significant associations with disease development were observed for TLR9 1174 A/G, TLR9 1635 A/G and IFNG 2109G/A. The two loci in TLR9 were in LD in our study population (r²=0.96, D’=1.00). A combined effect of the genotypes associated with increased risk of PTB (i.e. TLR9 1174G/G and IFNG 2109 A/A) was found when comparing PTB patients with LTBI controls (p=0.004) but not with healthy controls without infection (p=0.433).

Conclusions

Potential associations between TLR9 and IFN-γ genetic polymorphisms and PTB were observed in a Chinese population which supports further study of the roles played by TLR9/IFN-γ pathway during the development of PTB.

Changes in tuberculin skin test positivity over 20 years in periurban shantytowns in Lima, Peru

A cross-sectional, community-based study was performed in 2012 with 428 residents of periurban shantytowns in Lima, Peru to study risk factors for and changes in latent tuberculosis infection in age-stratified groups compared with our data from the same region in 1990 (N = 219) and 2005 (N = 103). Tuberculin skin test positivity in these communities was highly prevalent at 52% overall, increased with age (P < 0.01) and was similar to 2005 (53%) and 1990 (48%). From 1990 to 2012, the prevalence of tuberculin positivity decreased in 5-14 and 15-24 year old groups (to 17% and 34%, respectively, both P < 0.05). However, this may be explained by cessation of Bacille Calmette-Guérin revaccination during this period, because Bacille Calmette-Guérin revaccination doubled tuberculin positivity. Over the same 22-year period, tuberculin positivity in the ≥ 25 year old group remained high (71%, P = 0.3), suggesting that prevalent latent tuberculosis infection persists in the adult population despite improving medical care and socioeconomic development in this region.

Prevalence of latent TB infection in HIV infected persons in the Sylvanus Olympio teaching hospital of Lomé

OBJECTIVE

Determine the prevalence of latent TB infection in HIV-infected people.

METHOD

Using a cross-sectional study on HIV-infected persons monitored in the Department of Lung and Infectious Diseases of CHU Sylvanus Olympio of Lomé from August 10, 2010 to November 10, 2010. All patients are receiving anti-retroviral therapy and have no clinical or radiological symptoms of TB, and had never received tuberculin skin test (TST) in the last 3months. The CD4 rate of all patients was more than 200cells/μl. The diagnosis of latent TB infection is based on the measurement of at least 5mm of skin induration, 72h after a subcutaneous injection of 5IU of purified tuberculin.

RESULTS

One hundred and fifty four persons were included in the study, of which 107 were female and 47 were male. The median age was 40years old. Eleven patients were exposed to a risk of TB and only 70.7% of patients had a BCG scar. A suspicion of former TB was found in 18.8% of patients and approximately 45% of patients were very immunocompromised with a CD4 rate between 200 and 350; 117 patients had a positive TST. This represents an overall prevalence of 76% of latent TB infection.

CONCLUSION

The prevalence of latent TB infection obtained with the TST is high in this study. A similar study using the interferon-gamma release assay, which is more specific, would be more helpful to obtain more reliable epidemiological data on patient outcomes and to determine the appropriateness of the use of chemoprophylaxis with isoniazid.

Relevance of latent TB infection in areas of high TB prevalence

About one-third of the world population has latent TB infection (LTBI), the majority of which is distributed in 22 high-burden countries. Early diagnosis and treatment of active TB remains the top priority in resource-poor countries with high TB prevalence. Notwithstanding, because LTBI contributes significantly to the pool of active TB cases later on, its diagnosis and treatment is essential, especially in high-risk groups. The lack of a gold standard and several limitations of currently available tools, namely the tuberculin skin test and interferon-γ release assays, are major constraints for LTBI diagnosis. In areas with high TB prevalence, interferon-γ release assays have not shown superiority over the conventional tuberculin skin test and are yet to be systematically studied. Decisions regarding LTBI treatment with isoniazid preventive therapy should be made, keeping in mind the high prevalence of isoniazid resistance in these settings. Although efforts to shorten the LTBI treatment duration are encouraging, most trials have focused on adherence and toxicity. Future trials on short-duration regimens in high-burden settings should address drug efficacy issues as well. LTBI management, therefore, should comprise a targeted screening approach and individualization of LTBI treatment protocols. In addition, efforts should focus on airborne infection control measures in high-burden countries. A high prevalence of drug-resistant TB, the HIV epidemic, and delays in the diagnosis of active TB cases are other major concerns in areas of high TB prevalence. There is ample space for further research in these countries, whose outcomes may strengthen future national guidelines.

Tuberculin skin test in bacille Calmette-Guérin-vaccinated children: how should we interpret the results?

BACKGROUND

The tuberculin skin test (TST) is the most useful method for the diagnosis of tuberculosis (TB). There is no evidence about the effect of bacillus Calmette-Guerin (BCG) vaccine on the interpretation of TST results.

OBJECTIVE

The aim of this study was to evaluate TST results in a population of immigrants and adopted children, analyzing the effect of the vaccine on TST.

METHODS

Cross-sectional observational study including immigrants or adopted children evaluated in our unit between January 2003 and December 2008 was made. Children diagnosed with TB, live attenuated virus vaccinated 2 months earlier, HIV-infected, chronically ill, or under treatment with immunosuppressive agents were excluded. TST was considered the dependent variable. Independent variables were gender, age, geographical origin, BCG scar, nutritional status, immune status, and intestinal parasites infestation.

RESULTS

One thousand seventy-four children were included, 69.6 % are female; their origin includes China (34.7 %), Latin America (20.8 %), India/Nepal (19.4 %), Eastern Europe (15.7 %), and Africa (9.3 %). BCG scar was present in 79 % of children. Mantoux = 0 mm in 84.4 %, <10 mm in 4.1 %, and ≥10 mm in 11.4 %. Only two variables, age and BCG scar, influenced TST result. Risk of a TST false-positive due to BCG disappears 3 years after vaccine administration.

CONCLUSIONS

A history of BCG vaccination at birth does not interfere with TST results in children >3 years old. Under 3 years of age, BCG does interfere with and may cause a false-positive TST result. In these cases, the use of interferon-gamma release assays (IGRAs) is recommended. If IGRAs are not available or when results are indeterminate, ignoring the antecedent of the vaccine is recommended.

Determinants of tuberculin reactivity among health care workers: Interpretation of positivity following BCG vaccination

OBJECTIVE

To determine the extent to which a history of Bacille Calmette-Guerin (BCG) vaccination influences the likelihood of positive tuberculin skin test (TST) results.

DESIGN

Cross-sectional survey using a hospital-based tuberculosis surveillance program.

SETTING

Health Sciences Centre, a tertiary care hospital in Winnipeg, Manitoba.

METHODS

The 476 health care workers (HCWs) who had TST as part of the surveillance program between 1993 and 1997 constituted the study population. The two-step test was done in 91% of the participants who did not have a positive initial test, defined as 10 mm or greater of induration. Data were gathered through chart review supplemented by a short questionnaire administered to the HCWs.

MAIN RESULTS

One hundred and thirty-eight HCWs (29%) had a positive TST. In a stepwise, multiple logistic model controlling for age, sex, job title, work area, age of receiving BCG, time since BCG and duration of employment, only a history of BCG vaccination (odds ratio [OR] 22; 95% CI 12 to 41) and birth outside of Canada (OR 2.6; 95% CI 1.4 to 5.8) were significantly associated with a positive TST. When the definition of a positive TST was modified by increments of 1 mm, from 10 mm up to 20 mm of induration in BCG recipients, BCG was associated with positive reactions with indurations up to 19 mm but not 20 mm or greater. The OR declined with each increment. Of the 84 HCWs who were documented to have at least 20 years between BCG vaccination and testing, 41 (49%) had positive reactions.

CONCLUSIONS

BCG vaccination can produce lasting tuberculin reactivity, and indurations of 19 mm or less may be due to the effects of the vaccine.

Evaluation of the detection of Mycobacterium tuberculosis with metabolic activity in culture-negative human clinical samples

Mycobacterium tuberculosis is assumed to remain in a quiescent state during latent infection, being unable to grow in culture. The aim of this study was to evaluate the detection of viable but non-cultivable bacilli with metabolic activity in human clinical samples using a procedure that is independent of the immunological status of the patient. The study was performed on 66 human clinical samples, from patients subjected to routine diagnosis to rule out a mycobacterial infection. Specimens from pulmonary and extra-pulmonary origins were verified to contain human DNA before testing for M. tuberculosis DNA, rRNA and transient RNA by real-time quantitative PCR. Clinical records of 55 patients were also reviewed. We were able to detect viable but non-cultivable bacilli with a metabolic activity in both pulmonary and extra-pulmonary samples. Mycobacterium tuberculosis RNA was detected in the majority of culture-positive samples whereas it was detected in one-third of culture-negative samples, 20% of them showed metabolic activity. Amplifications of the ftsZ gene and particularly of the main promoter of the ribosomal operon rrnA, namely PCL1, seem to be good targets to detect active bacilli putatively involved in latent infection. Moreover, this last target would provide information on the basal metabolic activity of the bacilli detected.

Interferon gamma release assay compared with the tuberculin skin test for latent tuberculosis detection in pregnancy

OBJECTIVE

To estimate agreement and correlation between the tuberculin skin test and an interferon gamma release assay for detecting latent tuberculosis (TB) infection in pregnant women.

METHODS

We conducted a cross-sectional study of pregnant women initiating prenatal care at a university-affiliated public hospital between January 5, 2009, and March 15, 2010. Eligible women received a questionnaire about TB history and risk factors as well as the tuberculin skin test and phlebotomy for the interferon gamma release assay. Agreement and correlation between tests were estimated, and different cutoffs for interferon gamma release assay positivity were used to assess effect on agreement. Furthermore, predictors of test positivity and test discordance were evaluated using multivariable analysis.

RESULTS

Of the 220 enrolled women, 199 (90.5%) returned for tuberculin skin test evaluation. Over 70% were Hispanic and 65% were born in a country with high TB prevalence. Agreement between the tuberculin skin test and interferon gamma release assay was 77.39 (κ=0.26). This agreement was not significantly changed using different cutoffs for the assay. Birth bacille Calmette-Guérin vaccination was associated with tuberculin skin test positivity (odds ratio [OR] 4.33, 95% confidence interval [CI] 1.4-13.48, P=.01), but not interferon gamma release assay positivity. There were no statistically significant predictors of the tuberculin skin test and interferon gamma release assay result discordance; however, birth in a high-prevalence country was marginally associated with tuberculin skin test-positive and interferon gamma release assay-negative results (OR 2.94, 95% CI 0.86-9.97 P=.08).

CONCLUSION

Comparing the tuberculin skin test and interferon gamma release assay results in pregnancy, concordance and agreement were poor. Given that much is still unknown about the performance of interferon gamma release assays in pregnancy, further research is necessary before the tuberculin skin test is abandoned for screening of latent TB infection in pregnancy.

LEVEL OF EVIDENCE

III.

The tuberculin skin test is unreliable in school children BCG-vaccinated in infancy and at low risk of tuberculosis infection

BACKGROUND

The tuberculin skin test (TST) is often used to screen for latent tuberculosis infection (LTBI) in school children, many of whom were bacille Calmette-Guérin (BCG)-vaccinated in infancy. The reliability of the TST in such children is unknown.

METHODS

TSTs performed in low-risk BCG-vaccinated and -nonvaccinated grade 1 and grade 6 First Nations (North American Indian) school children in the province of Alberta, Canada, were evaluated retrospectively. To further assess the specificity of the TST, BCG-vaccinated children with a positive TST (≥10 mm of induration) and no treatment of LTBI were administered a QuantiFERON-TB Gold In-Tube test (QFT-GIT, Cellestis International).

RESULTS

A total of 3996 children, 2063 (51.6%) BCG-vaccinated and 1933 (48.4%) BCG-nonvaccinated, were screened for LTBI. Vaccinated children were more likely than nonvaccinated children to be TST positive (5.7% vs. 0.2%, P < 0.001). Vaccinated children with a positive TST were more likely to have a recent past TST as compared with those with a negative TST (6.8% versus 2.8%, P = 0.01). Among 65 BCG-vaccinated TST-positive children who underwent a QFT-GIT, only 5 (7.7%; 95% CI: 2.5%, 17.0%) were QFT-GIT positive. A TST of ≥15 mm was more likely to be associated with a positive QFT-GIT than a TST of 10 to 14 mm, 16.0% (95% CI: 4.5%, 36.1%) versus 2.5% (95% CI: 0.1%, 13.2%), P = 0.047.

CONCLUSION

The TST is unreliable in school children, BCG-vaccinated in infancy, and who are at low risk of infection. The QFT-GIT is a useful confirmatory test for LTBI in BCG-vaccinated TST-positive school children.

Diagnosis of latent tuberculosis: Can we do better?

Latent tuberculosis infection (LTBI) is often diagnosed by the tuberculin skin test (TST). The latter has several limitations with regard to its sensitivity and specificity. It may be positive in people with prior bacille Calmette-Guérin (BCG) vaccination or exposure to nontuberculous mycobacteria. False negative TST results frequently occur in patients with impaired T-cell function. Therefore TST results have to be interpreted taking into consideration the pretest risk of TB infection or reactivation. Recently, interferon gamma release assays (IGRA) were introduced for the diagnosis of LTBI. These include the T-SPOT-TB and the QuantiFERON^®-TB Gold tests.These tests measure interferon gamma released in response to T-cell stimulation by specific Mycobacterium tuberculosis antigens. These tests have been shown to be more specific than the TST as they are not affected by BCG vaccination. Their sensitivity was similar to that of the TST and in some studies they correlated better with the degree of exposure. In immune-compromised patients their sensitivity was better than that of the TST. IGRA tests were shown to have better predictive value for the development of active disease among individuals with LTBI. These tests are expensive. Their most cost-effective utilization is as confirmatory tests in patients with positive TST results, particularly in areas with high rates of BCG vaccination.

[Specific features of tuberculosis in childhood]

Primary infection with Mycobacterium tuberculosis usually occurs during childhood. The source of infection is most often an adult. The risk of infection in exposed children is modulated by various factors related to the infectiousness of the index case, exposure conditions, and the child himself. This review aims to describe the specific diagnostic and therapeutic features of latent TB infection and TB disease in childhood.

The tuberculin skin test (TST) is affected by recent BCG vaccination but not by exposure to non-tuberculosis mycobacteria (NTM) during early life

The tuberculin skin test (TST) is widely used in TB clinics to aid Mycobacterium tuberculosis (M.tb) diagnosis, but the definition and the significance of a positive test in very young children is still unclear. This study compared the TST in Gambian children at 4½ months of age who either received BCG vaccination at birth (Group 1) or were BCG naïve (Group 2) in order to examine the role of BCG vaccination and/or exposure to environmental mycobacteria in TST reactivity at this age. Nearly half of the BCG vaccinated children had a positive TST (≥5 mm) whereas all the BCG naïve children were non-reactive, confirming that recent BCG vaccination affects TST reactivity. The BCG naïve children demonstrated in vitro PPD responses in peripheral blood in the absence of TST reactivity, supporting exposure to and priming by environmental mycobacterial antigens. Group 2 were then vaccinated at 4½ months of age and a repeat TST was performed at 20–28 months of age. Positive reactivity (≥5 mm) was evident in 11.1% and 12.5% infants from Group 1 and Group 2 respectively suggesting that the timing of BCG vaccination had little effect by this age. We further assessed for immune correlates in peripheral blood at 4½ months of age. Mycobacterial specific IFNγ responses were greater in TST responders than in non-responders, although the size of induration did not correlate with IFNγ. However the IFNγ: IL-10 ratio positively correlated with TST induration suggesting that the relationship between PPD induced IFNγ and IL-10 in the peripheral blood may be important in controlling TST reactivity. Collectively these data provide further insights into how the TST is regulated in early life, and how a positive response might be interpreted.

Referrals for positive tuberculin tests in new health care workers and students: a retrospective cohort study

BACKGROUND

Documentation of test results for latent tuberculosis (TB) infection is important for health care workers and students before they begin work. A negative result provides a baseline for comparison with future tests. A positive result affords a potential opportunity for treatment of latent infection when appropriate. We sought to evaluate the yield of the referral process for positive baseline tuberculin tests, among persons beginning health care work or studies.

METHODS

Retrospective cohort study. We reviewed the charts of all new health care students and workers referred to the Montreal Chest Institute in 2006 for positive baseline tuberculin skin tests (> or =10 mm). Health care workers and students evaluated for reasons other than positive baseline test results were excluded.

RESULTS

630 health care students and workers were evaluated. 546 (87%) were foreign-born, and 443 (70%) reported previous Bacille Calmette-Guérin (BCG) vaccination. 420 (67%) were discharged after their first evaluation without further treatment. 210 (33%) were recommended treatment for latent TB infection, of whom 165 (79%) began it; of these, 115 (70%) completed adequate treatment with isoniazid or rifampin. Treatment discontinuation or interruption occurred in a third of treated subjects, and most often reflected loss to follow-up, or abdominal discomfort. No worker or student had active TB.

CONCLUSIONS

Only a small proportion of health care workers and students with positive baseline tuberculin tests were eligible for, and completed treatment for latent TB infection. We discuss recommendations for improving the referral process, so as to better target workers and students who require specialist evaluation and treatment for latent TB infection. Treatment adherence also needs improvement.

Annual incidence of latent tuberculosis infection among newly employed nurses at a tertiary care university hospital

OBJECTIVE

To investigate the annual rate of tuberculosis (TB) infection among newly employed nurses using both tuberculin skin test (TST) and QuantiFERON-TB Gold (QFT-G; Cellestis Limited) assay.

DESIGN

A prospective cohort study involving newly employed nurses.

SETTING

A tertiary care university hospital in South Korea.

METHODS

All participants (n = 196) were tested with the TST and QFT-G assay at baseline. After 1 year, the TST and QFT-G assay were reperformed for subjects who had negative TST results at baseline and for all subjects, respectively.

RESULTS

The baseline TST and QFT-G assays were positive for 101 subjects (51.5%) and 28 subjects (14.3%), respectively; 22 subjects (11.2%) had positive results of both tests. Although the overall between-test agreement was 54.9% (k = 0.151) [95% confidence interval, 0.047-0.245]), agreement improved to 78.5% (k = 0.462 [95% confidence interval, 0.007-0.917]) for subjects who had not received bacille Calmette-Guérin vaccination. After 1 year, the TST yielded positive results for 16 (21.3%) of 75 nurses with negative baseline results, and the QFT-G assay yielded positive results for 21 (14.4%) of 146 subjects with negative baseline results. Collectively, 5 subjects (3.0%) experienced conversion to positive results with both tests, and 32 subjects (18.9%) experienced conversion to positive results with one of the tests. Neither the employing hospital department nor exposure to patients with TB affected test conversion status.

CONCLUSIONS

The poor overall agreement between TST and QFT-G results may have been caused by the confounding effect of bacille Calmette-Guérin vaccination. The annual risk of TB infection among newly employed nurses was at least 3% on the basis of results of both the TST and QFT-G test. Stricter preventive strategies against TB spread should be implemented in our hospital.

Discrepancy between the tuberculin skin test and the levels of serum interferon-gamma in the diagnosis of tubercular infection in contacts

OBJECTIVE

Our aim was to compare the tuberculin skin test (TST) results and the level of serum IFN-gamma in the diagnosis of TB infection among contact of smear positive tuberculosis.

DESIGN AND METHODS

Chest x ray, tuberculin skin test and serum level of interferon-gamma (IFN-gamma) by ELISA were performed to 30 sputum positive tuberculosis patients, their 118 household contacts and 31 healthy controls.

RESULTS

The serum level of IFN-gamma was significantly elevated in index cases than in contacts and control groups. There was no statically significant difference in serum level of IFN-gamma between vaccinated and unvaccinated contacts. There was no significant correlation between IFN-gamma level and tuberculin reaction or induration diameter in vaccinated contacts. There was significant correlation between IFN-gamma level and tuberculin reaction or induration diameter in BCG unvaccinated contacts.

CONCLUSION

The serum IFN-gamma is a better indicator of the risk of mycobacterial infection than TST in BCG-vaccinated contacts.

Contact investigation in a primary school using a whole blood interferon-gamma assay

OBJECTIVES

To evaluate the usefulness of QuantiFERON-TB Gold (QFT-G) for children.

METHODS

Students in a primary school exposed to a tuberculosis patient were investigated using the tuberculin skin test (TST), chest X-ray examination and sequential QFT-G tests.

RESULTS

The first QFT-G test was conducted one month after the end of exposure for 308 of the 313 children, with 6 (1.9%) positive. TST results were obtained from 306 of the students at 2 months after exposure, and 200 (65.4%) had induration > or =5mm. A second QFT-G test, a further month later, and a third QFT-G test, six months after exposure, found an additional 2 positive and one weakly positive, respectively. Overall, the rate of QFT-G positivity was 9.8% (4/41) for close contact children (> or =90h exposure), significantly higher than for casual contacts (< or =18h exposure; 1.8%, 5/272; p=0.020), whereas there was no significant difference in TST positive rates (p=0.078).

CONCLUSIONS

These data suggest that QFT-G has the same performance characteristics in BCG vaccinated children as it does in adults. The observation that none of the 297 students who were QFT-G negative had developed active TB after 3 years of follow-up suggests that QFT-G has a very high negative predictive value.

Lymphocyte proliferation to mycobacterial antigens is detectable across a spectrum of HIV-associated tuberculosis

Background

Identifying novel TB diagnostics is a major public health priority. We explored the diagnostic characteristics of antimycobacterial lymphocyte proliferation assays (LPA) in HIV-infected subjects with latent or active TB.

Methods

HIV-infected subjects with bacille Calmette Guérin (BCG) scars and CD4 counts ≥ 200 cells/mm³ entering a TB booster vaccine trial in Tanzania had baseline in vivo and in vitro immune tests performed: tuberculin skin tests (TST), LPA and five day assays of interferon gamma (IFN-γ) release. Assay antigens were early secreted antigenic target 6 (ESAT-6), antigen 85 (Ag85), and Mycobacterium tuberculosis whole cell lysate (WCL). Subjects were screened for active TB at enrollment by history, exam, sputum smear and culture. We compared antimycobacterial immune responses between subjects with and without latent or active TB at enrollment.

Results

Among 1885 subjects screened, 635 had latent TB and 13 had active TB. Subjects with latent TB were more likely than subjects without TB to have LPA responses to ESAT-6 (13.2% vs. 5.5%, P < 0.0001), Ag85 (18.7% vs. 3.1%, P < 0.0001), and WCL (45.7% vs. 17.1%, P < 0.0001). Subjects with active TB also were more likely than those without active TB to have detectable LPA responses to ESAT-6 (38.5% vs. 8.1%, P = 0.0001), Ag85 (46.2% vs. 8.5%, P < 0.0001), and WCL (61.5% vs. 27.0%, P = 0.0053). In subjects with a positive TST, LPA responses to ESAT-6, Ag85 and WCL were more common during active TB (p < 0.0001 for all tests). In diagnosing active TB, in vivo and in vitro tests of mycobacterial immune responses had sensitivity and specificity as follows: TST 84.6% and 65.5%, ESAT-6 LPA 38.5% and 92.0%, Ag85 LPA 46.2% and 91.5%, and WCL LPA 61.5% and 73.0%. Detectable LPA responses were more common in patients with higher CD4 counts, and higher HIV viral loads.

Conclusion

Lymphoproliferative responses to mycobacteria are detectable during HIV-associated active TB, and are less sensitive but more specific than TST.

Trial registration

ClinicalTrials.gov Identifier NCT00052195.

Interpretation of repeat tuberculin skin testing in international adoptees: conversions or boosting

BACKGROUND

Internationally-adopted children are a unique group of Bacille Calmette-Guérin (BCG)-vaccinated children with high rates of latent tuberculosis infection (LTBI) in whom serial tuberculin skin tests (TST) are recommended. No study has measured the incidence of TST conversion in these children.

METHODS

Internationally-adopted children completed baseline and follow-up TST to measure the incidence of Mycobacterium tuberculosis infection and factors associated with TST conversion. Data were collected regarding age, gender, birth country, vaccination history, history of tuberculosis (TB) exposure, previous TB screening, and preadoptive environment. All children completed physical examinations including a standardized evaluation for TB, anthropometric assessment, and documentation of BCG scar.

RESULTS

Fourteen percent of children (N = 390) had evidence of LTBI at baseline. Children were more likely to have LTBI if they were older, BCG vaccinated, or had been in the United States longer. An additional 13% of children had TST indurations > or = 10 mm at follow-up testing. Regardless of BCG vaccination status or nutritional status, children who were younger at baseline were more likely to have a TST induration > or = 10 mm at follow-up.

CONCLUSIONS

International adoptees have significant risk of LTBI. Although our findings suggest that recent infection with M. tuberculosis led to TST conversion in some children, the increase in follow-up TST induration could also be attributed to TST boosting resulting from prior BCG vaccination. When serial TST testing is completed in young, BCG-vaccinated children, interpretation of the follow-up TST should consider baseline TST results.

Tuberculosis screening of travelers to higher-incidence countries: a cost-effectiveness analysis

Background

Travelers to countries with high tuberculosis incidence can acquire infection during travel. We sought to compare four screening interventions for travelers from low-incidence countries, who visit countries with varying tuberculosis incidence.

Methods

Decision analysis model: We considered hypothetical cohorts of 1,000 travelers, 21 years old, visiting Mexico, the Dominican Republic, or Haiti for three months. Travelers departed from and returned to the United States or Canada; they were born in the United States, Canada, or the destination countries. The time horizon was 20 years, with 3% annual discounting of future costs and outcomes. The analysis was conducted from the health care system perspective. Screening involved tuberculin skin testing (post-travel in three strategies, with baseline pre-travel tests in two), or chest radiography post-travel (one strategy). Returning travelers with tuberculin conversion (one strategy) or other evidence of latent tuberculosis (three strategies) were offered treatment. The main outcome was cost (in 2005 US dollars) per tuberculosis case prevented.

Results

For all travelers, a single post-trip tuberculin test was most cost-effective. The associated cost estimate per case prevented ranged from $21,406 for Haitian-born travelers to Haiti, to $161,196 for US-born travelers to Mexico. In all sensitivity analyses, the single post-trip tuberculin test remained most cost-effective. For US-born travelers to Haiti, this strategy was associated with cost savings for trips over 22 months. Screening was more cost-effective with increasing trip duration and infection risk, and less so with poorer treatment adherence.

Conclusion

A single post-trip tuberculin skin test was the most cost-effective strategy considered, for travelers from the United States or Canada. The analysis did not evaluate the use of interferon-gamma release assays, which would be most relevant for travelers who received BCG vaccination after infancy, as in many European countries. Screening decisions should reflect duration of travel, tuberculosis incidence, and commitment to treat latent infection.