Latent tuberculosis infection in healthcare workers in low- and middle-income countries: an updated systematic review

Healthcare workers (HCWs) are at increased risk of latent tuberculosis (TB) infection (LTBI) and TB disease.We conducted an updated systematic review of the prevalence and incidence of LTBI in HCWs in low- and middle-income countries (LMICs), associated factors, and infection control practices. We searched MEDLINE, Embase and Web of Science (January 1, 2005-June 20, 2017) for studies published in any language. We obtained pooled estimates using random effects methods and investigated heterogeneity using meta-regression.85 studies (32 630 subjects) were included from 26 LMICs. Prevalence of a positive tuberculin skin test (TST) was 14-98% (mean 49%); prevalence of a positive interferon-γ release assay (IGRA) was 9-86% (mean 39%). Countries with TB incidence ≥300 per 100 000 had the highest prevalence (TST: pooled estimate 55%, 95% CI 41-69%; IGRA: pooled estimate 56%, 95% CI 39-73%). Annual incidence estimated from the TST was 1-38% (mean 17%); annual incidence estimated from the IGRA was 10-30% (mean 18%). The prevalence and incidence of a positive test was associated with years of work, work location, TB contact and job category. Only 15 studies reported on infection control measures in healthcare facilities, with limited implementation.HCWs in LMICs in high TB incidence settings remain at increased risk of acquiring LTBI. There is an urgent need for robust implementation of infection control measures.

Prevalence and associated risk factors of latent tuberculosis infection among undergraduate and postgraduate dental students: A retrospective study

To estimate the prevalence of latent tuberculosis (TB) infection (LTBI) in Italian dental students exposed to the same occupational risks as dental health care personnel and to evaluate potential risk factors, a cross-sectional study was conducted on undergraduate and postgraduate students. After clinical evaluation, students were given a tuberculin skin test; in those found positive, an interferon-γ release assay (IGRA) was conducted. Of the 281 students enrolled, 10 were only TST positive; 8 were TST or/and IGRA positive. We found that participants testing positive at TST and/or IGRA, a group in which the risk of false LTBI positives is minimal, were older and had been studying longer. Although the prevalence of LTBI among dental students in our study was low, a risk of acquiring a work-related infection exists even in a country with a low incidence of TB. Thus, dental students should be screened to catch LTBI early on.

Latent tuberculosis infection among a large cohort of medical students at a teaching hospital in Italy

The surveillance of latent tuberculosis infection (LTBI) in both healthcare workers and healthcare students is considered fundamental for tuberculosis (TB) prevention. The aim of the present study was to estimate LTBI prevalence and evaluate potential risk-factors associated with this condition in a large cohort of medical students in Italy. In a cross-sectional study, performed between March and December 2012, 1511 eligible subjects attending the Medical School 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 confirmed with an interferon-gamma release assay (IGRA). A standardized questionnaire was collected for multivariate risk analysis. A total of 1302 (86.2%) students underwent TST testing and completed the questionnaire. Eleven subjects (0.8%) resulted TST positive and LTBI diagnosis was confirmed in 2 (0.1%) cases. Professional exposure to active TB patients (OR 21.7, 95% CI 2.9-160.2; P value 0.003) and previous BCG immunization (OR 28.3, 95% CI 3.0-265.1; P value 0.003) are independently associated with TST positivity. Despite the low prevalence of LTBI among Italian medical students, an occupational risk of TB infection still exists in countries with low circulation of Mycobacterium tuberculosis.

Tuberculin skin test and QuantiFERON-TB Gold In-tube Test for latent tuberculosis in Thai HIV-infected adults

BACKGROUND AND OBJECTIVE

Limited data exist for the performance of QuantiFERON-TB Gold In-tube Test (QFT-IT) in comparison to tuberculin skin test (TST) for detecting latent tuberculosis (LTB) in patients with human immunodeficiency virus (HIV) infection from tuberculosis (TB)-endemic Asia-Pacific countries.

METHODS

A cohort study of Thai HIV-infected patients without history of TB or LTB treatment was conducted from March 2012 through March 2013. Each patient underwent simultaneous TST and QFT-IT.

RESULTS

Among the 150 enrolled subjects, the median age was 40 years (range 17-65), 53% were male, and the median CD4 count was 367 cells/μL (range 8-1290). Reactive TST and positive QFT-IT were 16% and 13%, respectively, with low concordance between tests (kappa = 0.26); correlation between TST reaction size and level of interferon-γ was moderate (r = 0.34). Independent factors associated with discordant results were long-term smoking (adjusted odds ratio (aOR) 5.74; P = 0.002) for TST-reactive, QFT-IT-negative subjects, and age greater than 52 years (aOR 5.56; P = 0.02) and female gender (aOR 4.40; P = 0.04) for TST non-reactive, QFT-IT-positive subjects. The level of agreement between both tests improved when using a TST cut-off of ≥ 10 mm (kappa = 0.39).

CONCLUSIONS

In our setting where QFT-IT is available but has limited use due to cost, TST with a cut-off of 10 mm for reactivity should be the initial LTB test. HIV-infected women and persons older than 52 years with non-reactive TST and long-term smokers with reactive TST may benefit from subsequent QFT-IT.

Prevalence of latent tuberculosis infection and associated risk factors among 3,374 healthcare students in Italy

Introduction

The risk of tuberculosis (TB) in healthcare personnel (HCP) is related to its incidence in the general population. Healthcare students involved in clinical training could be exposed to occupational risks similar to those that HCP face. The prevalence of latent tuberculosis infection (LTBI) among undergraduate healthcare students with different working seniority in Italy was analysed.

Methods

A cross-sectional study under a screening programme for LTBI among undergraduate and postgraduate students attending Medical School at the Second University of Naples was conducted between January 2012 and December 2013 with clinical evaluations, tuberculin skin testing (TST) and, in positive TST students, Interferon-γ release assays (IGRA). Putative risk factors for LTBI were assessed by means of a standardised questionnaire.

Results

3,374 students attending the Medical School of the Second University of Naples were submitted to a screening programme for TBC. 3,331 performed TST as a first-level test and 43 performed a Quantiferon test (QFT). 128 students were TST-positive and continued the diagnostic work with QFT, which was positive in 34 students. Of the 43 subjects who took the QFT as a first-level test only 1 was positive. In 35 students positive to the QFT test we formulated the diagnosis of LTBI by clinical and radiographic results. A correlation was found between age, non-Italian born persons, studying age, post-medical school status and LTBI.

Conclusions

The prevalence of LTBI among healthcare students in our study was very low. In countries with a low incidence of TB, the screening programmes of healthcare students can be useful for early identification and treatment of sporadic cases of LTBI.

Electronic supplementary material

The online version of this article (doi:10.1186/s12995-014-0034-5) contains supplementary material, which is available to authorized users.

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

BACKGROUND

The 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.

METHODS

In 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.

RESULTS

Seven 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).

CONCLUSIONS

The 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.

Transcriptional responses of host peripheral blood cells to tuberculosis infection

Host responses following exposure to Mycobacterium tuberculosis (TB) are complex and can significantly affect clinical outcome. These responses, which are largely mediated by complex immune mechanisms involving peripheral blood cells (PBCs) such as T-lymphocytes, NK cells and monocyte-derived macrophages, have not been fully characterized. We hypothesize that different clinical outcome following TB exposure will be uniquely reflected in host gene expression profiles, and expression profiling of PBCs can be used to discriminate between different TB infectious outcomes. In this study, microarray analysis was performed on PBCs from three TB groups (BCG-vaccinated, latent TB infection, and active TB infection) and a control healthy group. Supervised learning algorithms were used to identify signature genomic responses that differentiate among group samples. Gene Set Enrichment Analysis was used to determine sets of genes that were co-regulated. Multivariate permutation analysis (p < 0.01) gave 645 genes differentially expressed among the four groups, with both distinct and common patterns of gene expression observed for each group. A 127-probeset, representing 77 known genes, capable of accurately classifying samples into their respective groups was identified. In addition, 13 insulin-sensitive genes were found to be differentially regulated in all three TB infected groups, underscoring the functional association between insulin signaling pathway and TB infection.