Incidence Of Latent Tuberculosis Infection Research Articles

Tuberculosis among children visiting friends & relatives.

Most paediatric tuberculosis (TB) cases in low-TB-incidence countries involve children born to migrant families. This may be partially explained by trips to their countries of origin for visiting friends and relatives (VFR). We aimed to estimate the risk of latent TB infection (LTBI) and TB in children VFR. We conducted a prospective multicentric observational study in Catalonia (Spain) from 06/2017 to 12/2019. We enrolled children aged < 15years with a negative tuberculin skin test (TST) at baseline and at least one parent from a high-TB-incidence country, and who had travelled to their parent's birth country for ≥21days. TST and QuantiFERON-TB Gold Plus (QFT-Plus) were performed within 8-12weeks post-return. LTBI was defined as a TST ≥5mm and/or a positive QFT-Plus. Five hundred children completed the study, equivalent to 78.2 person-years of follow-up (PYFU). Thirteen children (2.6%) were diagnosed with LTBI (16.6/per100 PYFU,95%CI = 8.8-28.5), including two cases (0.4%) of TB (2.5/per100 PYFU, 95%CI = 0.3-9.3). LTBI incidence rates remained high after excluding BCG-vaccinated children (9.7/per100 PYFU,95%CI = 3.9-20.0). Household tobacco smoke exposure was associated with LTBI (aOR = 3.9, 95%CI = 1.1-13.3). The risk of LTBI in children VFR in high-TB-incidence countries may equal, or perhaps even exceed, the infection risk of the native population. The primary associated risk factor was the presence of smokers in the household. Furthermore, the incidence rate of active TB largely surpassed that of the countries visited. Children VFR in high-TB-incidence countries should be targeted for diagnostic and preventive interventions.

Screening for Latent Tuberculosis Infection using Interferon-Gamma Release Assay Test among Healthcare Workers

Healthcare workers (HCWs) represent a significant demographic for screening latent tuberculosis infection (LTBI) due to their potential exposure to infectious patients. Tests based on immunology detection, such as the tuberculin skin test (TST) and the interferon-gamma release assay (IGRA), have been pivotal in diagnosing LTBI. The objective of this study was to evaluate the efficacy of the IGRA test in detecting LTBI compared to the TST among HCWs in an infectious disease hospital. In a cross-sectional study conducted in August 2019 at the Sulianti Saroso Infectious Disease Hospital, we examined 84 HCWs selected through consecutive sampling. Participants were assessed using questionnaires, and the IGRA and TST tests were performed. The findings revealed that 42 (50%) HCWs tested positive for LTBI based on the IGRA test. Most were female, aged 36-45 years, had direct exposure to TB patients, and had been in the healthcare profession for over a decade. The concordance between the TST and IGRA test, as indicated by a κ value, was 0.234. Furthermore, a significant correlation was observed between the incidence of LTBI and the duration of the healthcare profession (p=0.016). In conclusion, our research suggests that both TST and IGRA tests can effectively detect LTBI. The IGRA test had a higher positivity rate among HCWs with over ten years of service.

84. Prevalence and incidence of latent tuberculosis infection among healthcare workers in chest diseases hospitals, Bangladesh: Putting infection control into context

84. Prevalence and incidence of latent tuberculosis infection among healthcare workers in chest diseases hospitals, Bangladesh: Putting infection control into context

The effect of BCG vaccination and risk factors for latent tuberculosis infection among college freshmen in China

ObjectivesIn this study, we aimed to verify whether Bacillus Calmette–Guérin (BCG) can protect first-year college students against Mycobacterium tuberculosis (MTB) infection by the recombinant fusion protein ESAT6-CFP10 skin test (ECST) or the tuberculin skin test (TST). MethodsWe conducted a cross-sectional study to assess risk factors for latent tuberculosis infection (LTBI). Vaccine effectiveness of BCG against LTBI, measured by ECST and TST separately, was assessed using multivariable logistic regression. ResultsA total of 7351 college freshmen accepted ECST, whereas 7228 accepted TST. A total of 263 (3.58%) tested positive with ECST and 581 (8.04%) tested positive with TST. BCG was significantly associated with LTBI (ECST: adjusted odds ratio (aOR) = 0.26; 95% CI 0.09 to 0.73; TST: aOR = 0.25; 95% CI 0.13 to 0.49). The BCG protective effect on freshmen living in rural areas (ECST: aOR = 0.16; 95% CI 0.04 to 0.55; TST: aOR = 0.12; 95% CI 0.04 to 0.33) is better than that of freshmen living in cities (ECST: aOR = 0.53; 95% CI 0.07 to 4.03; TST: aOR = 0.44; 95% CI 0.17 to 1.16). ConclusionsProtection against LTBI was strongly associated with BCG vaccination. A novel skin test (ECST) may underestimate the protective effects of BCG in college freshmen. BCG has better protection in areas with a slightly higher incidence of LTBI.

Phase I Trial Evaluating the Safety and Immunogenicity of Candidate TB Vaccine MVA85A, Delivered by Aerosol to Healthy M.tb-Infected Adults

The immunogenicity of the candidate tuberculosis (TB) vaccine MVA85A may be enhanced by aerosol delivery. Intradermal administration was shown to be safe in adults with latent TB infection (LTBI), but data are lacking for aerosol-delivered candidate TB vaccines in this population. We carried out a Phase I trial to evaluate the safety and immunogenicity of MVA85A delivered by aerosol in UK adults with LTBI (NCT02532036). Two volunteers were recruited, and the vaccine was well-tolerated with no safety concerns. Aerosolised vaccination with MVA85A induced mycobacterium- and vector-specific IFN-γ in blood and mycobacterium-specific Th1 cytokines in bronchoalveolar lavage. We identified several important barriers that could hamper recruitment into clinical trials in this patient population. The trial did not show any safety concerns in the aerosol delivery of a candidate viral-vectored TB vaccine to two UK adults with Mycobacterium tuberculosis (M.tb) infection. It also systemically and mucosally demonstrated inducible immune responses following aerosol vaccination. A further trial in a country with higher incidence of LTBI would confirm these findings.

RISK FACTORS OF LATENT TUBERCULOSIS INFECTION IN HEALTHCARE WORKERS AT HOSPITALS IN JEMBER CITY INDONESIA.

Background:Healthcare workers in Tuberculosis (TB) and non-TB units in hospitals have a high risk of experiencing Latent Tuberculosis Infection (LTBI), because of exposure to droplets containing Mycobacterium tuberculosis. This study aims to prove LTBI incidence and risk factors to healthcare workers at the hospital in Jember City.Material and Methods:a cross-sectional study, from January to March 2020 in two hospitals in Jember City. Healthcare workers in the TB care and non-TB care unit were examined using Tuberculin skin test (TST) with a cut off ≥ 10 mm for positive LTBI. Chest x-ray and clinical examination to rule out active TB and a standardized questionnaire were also used.Results:128 healthcare workers completed the questionnaires, clinical, tuberculin skin test (TST), and chest x-ray data. LTBI incidence of positive results 61.7% (n = 79). Contacts TB in the workplace (p value = 0.219; OR = 1.643; CI = 0.742-3.641) and a unit of work (p value = 0.102; OR = 0.760; CI = 0.559-1.031) has no relationship with LTBI. The profession (p value = 0.020; OR = 1.112; CI = 0.896-1.403), the duration of the work (p value = 0.039; OR = 2.984; CI = 1.067-8.342), and BCG immunization (p value =0.000; OR = 0.151; CI = 0.052-0.438) have important relationships with LTBI.Conclusion:TB infection with a high incidence, a risk of transmission to healthcare workers, and a relationship between occupational risk factors and LTBI among healthcare workers in Jember City, Indonesia have been established in this study.

Risk of latent and active tuberculosis infection in travellers: a systematic review and meta-analysis.

Achieving tuberculosis (TB) elimination in low TB incidence countries requires identification and treatment of individuals at risk for latent TB infection (LTBI). Persons travelling to high TB incidence countries are potentially at risk for TB exposure. This systematic review and meta-analysis estimates incident LTBI and active TB among individuals travelling from low to higher TB incidence countries. Five electronic databases were searched from inception to 18 February 2020. We identified incident LTBI and active TB among individuals travelling from low (<10 cases/100 000 population) to intermediate (10-100/100 000) or high (>100/100 000) TB incidence countries. We conducted a meta-analysis and meta-regression using a random effects model of log-transformed proportions (cumulative incidence). Subgroup analyses investigated the impact of travel duration, travel purpose and TB incidence in the destination country. Our search identified 799 studies, 120 underwent full-text review, and 10 studies were included. These studies included 1 154 673 travellers observed between 1994 and 2013, comprising 443 health care workers (HCW), 1 068 636 military personnel and 85 594 general travellers/volunteers. We did not identify any studies that estimated incidence of LTBI or active TB among people travelling to visit friends and relatives (VFRs). The overall cumulative incidence of LTBI was 2.3%, with considerable heterogeneity. Among individuals travelling for a mean/median of up to 6months, HCWs had the highest cumulative incidence of LTBI (4.3%), whereas the risk was lower for military (2.5%) and general travellers/volunteers (1.6%). Meta-regression did not identify a difference in incident LTBI based on travel duration and TB incidence in the destination country. Five studies reported cases of active TB, with an overall pooled estimate of 120.7 cases per 100 000 travellers. We found that travelling HCWs were at highest risk of developing LTBI. Individual risk activities and travel purpose were most associated with risk of TB infection acquired during travel.

Latent Tuberculosis Infection Increases in Kidney Transplantation Recipients Compared With Transplantation Candidates: A Neglected Perspective in Tuberculosis Control.

BackgroundThe prevalence and incidence of latent tuberculosis infection (LTBI) in patients with kidney transplantation remain unclear.MethodsIn this prospective study, we enrolled kidney transplantation candidates (KTCs) and recipients (KTRs) from 2014 to 2018. We defined LTBI as a positive result of QuantiFERON-TB Gold In-tube (QFT). We analyzed the predictors for LTBI acquisition and followed up on QFT assay test for 2 years among those initially without LTBI.ResultsOf 425 patients enrolled, 305 (71.8%) patients belonged to the KTC group and 120 (28.2%) to the KTR group. The initial QFT showed positive results in 32 (10.5%) and 24 (20.0%) patients in the KTC and KTR groups, respectively (P = .009). The QFT response value in patients with LTBI was higher in the KTR group than in the KTC group (1.85 vs 1.06 IU/mL, P = .046). Multivariate logistic regression showed that old age, absence of bacillus Calmette–Guérin (BCG) scar, presence of donor-specific antibody, and KTR group were independent factors for positive LTBI. For participants with initial negative QFT, positive QFT conversion within a 2-year follow-up was higher after kidney transplantation (20%) than in KTCs (5.5%) (P = .034).ConclusionsThis study is the first cohort to follow up LTBI status in patients with kidney transplantation and shows its higher prevalence and incidence in KTRs. It indicates that surveillance of LTBI after renal transplantation is important. In addition to status of kidney transplantation, old age, no BCG vaccination, and positive donor-specific antibody are also positive predictors for LTBI.

Latent Tuberculosis in Hematopoietic Stem Cell Transplantation: Diagnostic and Therapeutic Strategies to Prevent Disease Activation in an Endemic Population.

Latent tuberculosis infection (LTBI) affects one-fourth of the world´s population. Hematopoietic stem cell transplantation (HSCT) recipients are at an elevated risk of developing active tuberculosis infection (ATBI). In this retrospective study of donors and HSCT recipients who underwent transplantation between February 2000 and June 2018, our aim was to determine the prevalence of LTBI and ATBI and to describe diagnostic and therapeutic strategies in an HSCT population in an endemic region. The cohort of 409 participants included 125 allogeneic HSCT (allo-HSCT) recipients, 165 autologous HSCT (auto-HSCT) recipients, and 119 HSCT donors. Patients were evaluated pre-HSCT with tuberculin skin test and thoracic imaging. LTBI was diagnosed in 26.2% of the cohort. Cases represented 20% of the auto-HSCT population, 20% of the allo-HSCT population, and 41.2% of the donor population. Pre-HSCT evaluation to rule out ATBI was performed in 62.6% of the cohort; all results were negative. Isoniazid was administered to 73.3% of those with LTBI. Within subgroups, 91.7% of HSCT recipients and 51% of donors received treatment. The median duration of therapy pre-HSCT was 70 days in recipients and 48 days in donors. The incidence of post-HSCT ATBI was 0 at 1-year follow-up. The incidence of LTBI in our population was higher than expected and still might have been underestimated owing to diagnostic test limitations. The absence of incident ATBI suggests that recipients, as opposed to donors, must receive LTBI treatment. Prevention of infectious complications in the HSCT population should be prioritized to improve clinical outcomes. Prospective data from collaborative working groups is needed to determine the best diagnostic and therapeutic approaches in this vulnerable patient population.

Incidence of latent tuberculosis infection among health science students during clinical training.

BACKGROUND:The prevalence of latent tuberculosis infection (LTBI) has been found to be high among students undergoing clinical training. The aim of this study is to determine the incidence of LTBI among undergraduate health science students after their clinical training and to compare the risk between different college specialties.METHODS:This is a retrospective cohort study of students who completed their clinical training from 2010 to 2017. The risk of LTBI was defined based on the conversion of tuberculin skin test (TST) results from negative at the start of training to positive after the completion of training.RESULTS:A total of 2000 students were evaluated, of whom 1997 were included in this analysis. Six percent tested positive in the first TST of the initial screening. Ten percent of students with a normal baseline TST converted to positive on the follow-up TST. Clinical training in the college of medicine increased the risk of LTBI by 76% (odds ratio: 1.76; 95% confidence interval: 1.04– 2.96; P = 0.03) compared to clinical training in other medical colleges.CONCLUSIONS:The risk of acquiring LTBI during clinical training in health science colleges is 10%. Students in the college of medicine are at significantly higher risk of LTBI than students of other health science specialties.

Monitorization of tuberculosis screening tests during anti-TNF- and #945; treatment in children with rheumatic diseases

Aim: We aimed to investigate the incidence of latent tuberculosis infection (LTBI) and seroconversion rate of LTBI screening tests under anti-TNF-α treatment, in our pediatric patients with chronic rheumatic diseases.Material and Methods: The data of 47 patients received anti-TNF-α treatment for different chronic rheumatic diseases between May-2015 and May-2018, were reviewed retrospectively. Demographics and clinical findings of the patients, as well as the treatments and their durations, were collected. The tuberculin skin test (TST) and Quantiferon-TB-Gold in-tube (QFT) test results at initiation and one year after the anti-TNF-α treatment were compared. Results: The study group included 38 (80.8%) patients with juvenile idiopathic arthritis, six (12.7%) with idiopathic uveitis, two (4.2%) with Behcet's disease related uveitis and one (2.1%) with juvenile dermatomyositis. For a period at least one year, 33 (70.2%) patients received etanercept, 12 (25.5%) received infliximab and two (4.2%) received adalimumab treatment. Before anti-TNF-α treatment, 31.9% of the patients were diagnosed with LTBI. After one year of treatment, it was found to be increased to 44.6%. During treatment, the seroconversion rate of the screening tests for LTBI was determined to be 12.7% (6/47).Conclusion: The seroconversion rate of screening tests for LTBI was found high in pediatric patients receiving anti-TNF-α treatment. Although the consistency between TST and QFT tests was found weak in our study, the fact that these tests should be used and evaluated together in the follow-up in the light of current guidelines in terms of LTBI and active tuberculosis development, remains still up to date. Further research is need in order for more enlightening data on the risk of LTBI and active tuberculosis in patients under anti-TNF-α treatment.

Recent trends in the incidence of latent tuberculosis infection in Japanese patients with lung cancer: A small retrospective study

Active tuberculosis is an important complication in Japanese lung cancer patients. We studied the generation-wise trend of latent tuberculosis infection (LTBI) among lung cancer patients. We analyzed background data including birth year, lung cancer status, and interferon-gamma release assay (IGRA) data of lung cancer patients who were admitted to National Hospital Organization Tokyo National Hospital from 2010 to 2016. Of the 1450 cases, 7 showed active tuberculosis and 45 had previous tuberculosis. Of the remaining 1398 patients, 795 underwent IGRAs and 120 (15%) of them were found to have LTBI. Patients with LTBI were older (p = 0.0005), and the proportion of smokers was also higher in this group (p = 0.0159) than among those without LTBI. LTBI incidence decreased from 33% among patients born in the 1920s to 21%, 15%, 9.8%, and 5.1% among those born in the 1930s, 1940s, 1950s, and after 1960, respectively. A significant decrease in the smoking adjusted risk ratio was also observed with every generation (p < 0.0001). Our study suggests that the total number of patients with active tuberculosis comorbid with lung cancer will greatly decrease in the future in Japan. However, owing to recent improvements in lung cancer prognosis due to advances in cancer medication, careful monitoring for active tuberculosis development may be required in lung cancer patients with LTBI.

Ambulatory independence is associated with higher incidence of latent tuberculosis infection in long-term care facilities in Taiwan.

Tuberculosis (TB) in the elderly population remains a major challenge in areas with intermediate disease burden like Taiwan. Despite the increasing burden and high risks of TB in the elderly population, particularly those living in long-term care facilities (LTCFs), diagnostic testing for latent tuberculosis infection (LTBI) has not been carefully evaluated in this group. This study aimed to investigate the prevalence and predictors of LTBI in older adults living in LTCFs. Older adults living in seven LTCFs in Taiwan were prospectively enrolled between January and July 2017. Interferon-gamma release assay (IGRA) through QuantiFERON-TB Gold In-tube was used to determine presence of LTBI. Predictors for LTBI were analyzed. A total of 258 participants were enrolled, including 240 older residents (mean age, 81.6 years; male, 51.2%) and 18 employees (mean age, 64.8 years; male, 22.2%). The proportion of independent status in ambulation assessments significantly declined with aging (p<0.001). The IGRA-positivity rate in LTCFs was 31.4% (81/258), which consisted of 73 (30.4%) residents and 8 (44.4%) employees. The IGRA results were different with respect to the ambulation status (p=0.052). In the multivariate logistic regression analysis, the only independent predictor of LTBI among older adults in LTCFs was independent ambulation (odds ratio, 2.16; 95% confidence interval, 1.09-4.28; p=0.027). There was a high prevalence of LTBI among older adults in LTCFs in Taiwan. Independent ambulation was the only independent predictor of LTBI.

High incidence of latent tuberculosis infection in indigent patients receiving biologics in New York City

High incidence of latent tuberculosis infection in indigent patients receiving biologics in New York City

High risk for latent tuberculosis infection among medical residents and nursing students in India.

Defining occupational latent tuberculosis infection (LTBI) risk among healthcare workers is needed to support implementation of prevention guidelines. Prospective cohort study of 200 medical residents and nursing students in India was conducted May 2016—December 2017. Tuberculin skin test (TST) and QuantiFERON TB Gold Test-in-tube (QFT-GIT) were performed at study entry and 12 months. Primary outcome was incident LTBI (≥10mm TST induration and/or ≥0.35IU/mL QFT-GIT) at 12 months; secondary outcomes included baseline LTBI prevalence and risk factors for incident and prevalent LTBI using Poisson regression. Among 200, [90 nursing students and 110 medical residents], LTBI prevalence was 30% (95% CI, 24–37); LTBI incidence was 26.8 (95% CI, 18.6–37.2) cases per 100 person-years and differed by testing method (28.7 [95% CI, 20.6–38.9] vs 17.4 [95% CI, 11.5–25.4] cases per 100 person-years using TST and QFT-GIT, respectively). Medical residents had two-fold greater risk of incident LTBI than nursing students (Relative Risk, 2.16; 95% CI, 1.05–4.42). During study period 6 (3%) HCWs were diagnosed with active TB disease. Overall, median number of self-reported TB exposures was 5 (Interquartile Range, 1–15). Of 60 participants with prevalent and incident LTBI who were offered free isoniazid preventive therapy (IPT), only 2 participants initiated and completed IPT. High risk for LTBI was noted among medical residents compared to nursing students. Self-reported TB exposure is underreported, and uptake of LTBI prevention therapy remains low. New approaches are needed to identify HCWs at highest risk for LTBI.

Risk of Tuberculosis Infection among Healthcare Workers in a Tertiary Care Hospital in Bengaluru City.

Introduction:Tuberculosis (TB) is an airborne communicable disease caused by Mycobacterium tuberculosis. Infection is most likely to occur when an individual is exposed to someone with pulmonary TB on a day-to-day basis, such as by living or working in close quarters with someone who has an active disease. This study was undertaken using reliable screening and investigation tools for assessing the incident latent tuberculosis infection (LTBI) among healthcare workers (HCWs).Methodology:This descriptive longitudinal study was conducted among 600 HCWs at a tertiary care hospital in Bengaluru city for a period of 1 year 4 months (March 2016–June 2017). All HCWs were stratified according to their work profile as doctors, nurses, laboratory technicians, nursing aides, pharmacists, laundry workers (only those who come in contact with patients), dietary workers (only those who come in contact with patients), and workers from housekeeping department. Study subjects were enrolled in proportion to their population size. The data were collected by administering TB screening questionnaire and performing tuberculin skin test (TST). All the subjects who had negative TST reaction were followed up after 1 year from March 2017 to June 2017.Results:The study subjects consisted of 600 HCWs with a mean age of 27.8 ± 7.1 years. Initially, 600 study subjects underwent TST, 2 of whom were not contactable between 48 and 72 h of test administration. Of the remaining 598 subjects, 120 (20.1%) had a positive TST reaction. After 1 year, of the 478 subjects who tested negative, 345 study subjects underwent the repeat TST and 67 (19.4%) of the study subjects had a positive TST reaction.Conclusion:The prevalence of LTBI was 20.1% and it was significantly associated with age, place of residence, education, work commute time, and mode of transport. The incidence of LTBI was 19.4% and it was significantly associated with gender, place of residence, education, work commute time, and marital status.

Latent tuberculosis infection among medical students in Malaysia

Objective: This study aimed to determine prevalence of latent tuberculosis infection among medical students and tuberculosis exposure at the health facilities. Methods: A cross-section of study year 1 (n=68) and year 5 (n=75) medical students in a local university were recruited for latent tuberculosis infection testing using QuantiFERON-TB Gold Plus and a questionnaire analyzed for multivariate risk. Results: The majority of the study were vaccinated with BCG. None of year 1 medical students were positive for latent tuberculosis infection, however, six (8.0%) year 5 students were tested positive for latent tuberculosis infection. A higher incidence of year 5 medical students claimed to be exposed to tuberculosis at health facility (65.3% vs. 4.4%) and a higher percentage reported contact with tuberculosis case over the preceding year compared to year 1 students (30.7% vs. 8.8%). Conclusion: We observed a higher incidence of latent tuberculosis infection and higher exposure to tuberculosis in health facilities among year 5 medical students. Baseline screening and monitoring for progression to tuberculosis infection may benefit tuberculosis management programs.

High prevalence of infection and low incidence of disease in child contacts of patients with drug-resistant tuberculosis: a prospective cohort study

ObjectiveWe aimed to measure the prevalence and incidence of latent tuberculosis infection (LTBI) and tuberculosis (TB) disease in children in close contact with patients with drug-resistant TB (DR-TB) in a...

Rates of latent tuberculosis infection in patients treated with TNF inhibitors for psoriasis: a retrospective chart review

Background: Although tuberculosis screening guidelines for psoriasis patients on TNF inhibitors exist, few studies have reported the prevalence of latent tuberculosis infection (LTBI) and conversion rates in this population.Objective: To determine the incidence of LTBI and active tuberculosis in patients with psoriasis receiving TNF inhibitor therapy.Methods: A total of 138 patients were included in our retrospective study of patients treated from September 2004 to September 2017. Tuberculin skin test was considered positive with an induration of greater than 5 mm. History of Bacillus Calmette-Guérin vaccination, follow-up tests and prophylaxis were recorded.Results: Among 99 biologic-naïve patients, 14 had LTBI before starting biologic therapy and five developed LTBI during TNF inhibitor therapy. One biologic-naïve patient developed LTBI, then active tuberculosis. Among 39 non-biologic-naïve patients, three had LTBI before starting any biologic therapy, and one developed LTBI during treatment.Limitations: Limitations include small sample size and limited information documented in the medical chart.Conclusions: LTBI appears to be prevalent among psoriasis patients. Screening for LTBI in patients on biologics may reduce risk of active tuberculosis; however, current methods may not be fully effective. Clinicians may need to use other tools including risk factor assessment to fully evaluate risk.

Negative latent tuberculosis at time of incarceration: identifying a very high-risk group for infection.

The main aim was to measure the incidence of latent tuberculosis infection (LTBI) and identify risk factors associated with infection. In addition, we determined the number needed to screen (NNS) to identify LTBI and active tuberculosis. We followed 129 prisoners for 2 years following a negative two-step tuberculin skin test (TST). The cumulative incidence of TST conversion over 2 years was 29·5% (38/129), among the new TST converters, nine developed active TB. Among persons with no evidence of LTBI, the NNS to identify a LTBI case was 3·4 and an active TB case was 14·3. The adjusted risk factors for LTBI conversion were incarceration in prison number 1, being formerly incarcerated, and overweight. In conclusion, prisoners have higher risk of LTBI acquisition compared with high-risk groups, such as HIV-infected individuals and children for whom LTBI testing should be performed according to World Health Organization guidance. The high conversion rate is associated with high incidence of active TB disease, and therefore we recommend mandatory LTBI screening at the time of prison entry. Individuals with a negative TST at the time of entry to prison are at high risk of acquiring infection, and should therefore be followed in order to detect convertors and offer LTBI treatment. This approach has a very low NNS for each identified case, and it can be utilized to decrease development of active TB disease and transmission.