Estimating the annual risk of tuberculosis infection and disease in southeast of iran using the bayesian mixture method

Seroepidemiologic evidence of Q fever and associated factors among workers in veterinary service laboratory in South Korea

The incidence of Q fever has rapidly increased in South Korea since 2015. This study was undertaken to investigate the seroprevalence and seroreactivity of Q fever and the risk factors associated with its seroprevalence among workers in the veterinary service laboratory (VSL) in South Korea. This seroepidemiologic study was conducted in a total of 661 human subjects out of 1,328 subjects working in 50 VSL existing in South Korea between July 15 and July 29, 2019. Data were collected by administering survey questionnaires and by analyzing collected blood samples to determine the presence of antibodies against Coxiella burnetii. The seroprevalence and seroreactivity of C. burnetii infection were determined based on serum titers as (phase II IgG ≥1:256 and/or IgM ≥1:16) and (phase II IgG ≥1:16 and/or IgM ≥1:16) as determined by indirect immunofluorescent assay. Work, work environment, behavioral risk and protective factors associated with seroprevalence of Q fever were assessed by employing multivariable logistic regression analysis. Among the 661, the seroprevalence and seroreactivity of C. burnetii infection were 7.9% and 16.0%, respectively. Multivariate logistic regression analysis showed the risk factors significantly associated with seroprevalence were the antemortem inspection of cattle, goats, or sheep (APR (adjusted prevalence ratio), 2.52; 95% CI, 1.23–4.70)), animal blood splashed into or around eyes (APR, 2.24; 95% CI, 1.04–4.41), and contact with animals having Q fever (APR, 6.58; 95% CI, 3.39–10.85) during the previous year. This study suggests the need for precautions when contact with cattle, goats, or sheep is expected, especially during the antemortem inspection, when dealing with C. burnetii infected animals, or when there is a risk of ocular contact with animal derivatives. Therefore, we recommend the consistent use of appropriate personal protective equipment and other protective measures including PPE treatment and washing of body surfaces after work to prevent C. burnetii infections among VSL staff in South Korea.

Defining an intermediate category of tuberculin skin test: A mixture model analysis of two high-risk populations from Kampala, Uganda

One principle of tuberculosis control is to prevent the development of tuberculosis disease by treating individuals with latent tuberculosis infection. The diagnosis of latent infection using the tuberculin skin test is not straightforward because of concerns about immunologic cross reactivity with the Bacille Calmette-Guerin (BCG) vaccine and environmental mycobacteria. To parse the effects of BCG vaccine and environmental mycobacteria on the tuberculin skin test, we estimated the frequency distribution of skin test results in two divisions of Kampala, Uganda, ten years apart. We then used mixture models to estimate parameters for underlying distributions and defined clinically meaningful criteria for latent infection, including an indeterminate category. Using percentiles of two underlying normal distributions, we defined two skin test readings to demarcate three ranges. Values of 10 mm or greater contained 90% of individuals with latent infection; values less than 7.2 mm contained 80% of individuals without infection. Contacts with values between 7.2 and 10 mm fell into an indeterminate zone where it was not possible to assign infection. We conclude that systematic tuberculin skin test surveys within populations at risk, combined with mixture model analysis, may be a reproducible, evidence-based approach to define meaningful criteria for latent tuberculosis infection.

The global prevalence of latent tuberculosis: a systematic review and meta-analysis

In 1999, the World Health Organization (WHO) estimated that one-third of the world's population had latent tuberculosis infection (LTBI), which was recently updated to one-fourth. However, this is still based on controversial assumptions in combination with tuberculin skin test (TST) surveys. Interferon-γ release assays (IGRAs) with a higher specificity than TST have since been widely implemented, but never used to estimate the global LTBI prevalence.We conducted a systematic review and meta-analysis of LTBI estimates based on both IGRA and TST results published between 2005 and 2018. Regional and global estimates of LTBI prevalence were calculated. Stratification was performed for low, intermediate and high TB incidence countries and a pooled estimate for each area was calculated using a random effects model.Among 3280 studies screened, we included 88 studies from 36 countries with 41 IGRA (n=67 167) and 67 TST estimates (n=284 644). The global prevalence of LTBI was 24.8% (95% CI 19.7-30.0%) and 21.2% (95% CI 17.9-24.4%), based on IGRA and a 10-mm TST cut-off, respectively. The prevalence estimates correlated well to WHO incidence rates (Rs=0.70, p<0.001).In the first study of the global prevalence of LTBI derived from both IGRA and TST surveys, we found that one-fourth of the world's population is infected. This is of relevance, as both tests, although imperfect, are used to identify individuals eligible for preventive therapy. Enhanced efforts are needed targeting the large pool of latently infected individuals, as this constitutes an enormous source of potential active tuberculosis.

Estimating the annual risk of tuberculosis infection in Japan from interferon-gamma release assay data

To assess tuberculosis transmission frequency at a population level, the age-dependent Mantoux test has been used widely to estimate the annual risk of infection (ARI) with Mycobacterium tuberculosis. However, the widespread Bacille Calmette-Guerin (BCG) immunization program implemented in Japan in the 20th century has made natural infections with M. tuberculosis difficult to distinguish from immune responses against this vaccine. Consequently, a recognized alternative method for measuring the frequency of primary infections, the interferon-gamma release assay (IGRA), which partially decays as a function of time after infection, is used. We aimed to estimate the ARI in Japan from IGRA data along with its response decay information using mathematical modeling. Devising a partial differential equation system, we computed the probability of IGRA positivity as a function of time and age, accounting for the time-varying force of infection and decay function of the IGRA response. Jointly estimating the force of infection and the parameters governing the decay function of the IGRA response, we found that the age-dependent increasing pattern of the IGRA response was captured by the proposed simple model, yielding estimates of the time-dependent force of infection. ARI decreased as a function of time in the study subjects for all geographic locations. By the year 2030, our model showed that the median age of infection is predicted to be delayed by 40-50 years compared with that in 1940. The geographic variations in the ARI were striking, ranging from under 0.1% to 0.6% in 2018, which echoes the longstanding notion of highly heterogeneous geographical tuberculosis transmission in Japan.

Estimating the prevalence of Positive Tuberculin Skin Test Reactions in General Population and High-risk Groups: A Meta-analysis

Results of tuberculin skin test (TST) surveys among different populations have been reported in many studies as a method for detecting primary Mycobacterium tuberculosis infection. Combining these results provides reliable estimates of primary latent tuberculosis (TB) infection for health policymakers. This study aims to estimate the prevalence of latent TB infection in general and high-risk populations in Iran. National and international databanks were searched using specific keywords. After restricting the search strategy, duplicates exclusion, reviewing titles, abstracts and full texts, and quality assessment, eligible papers were selected. The heterogeneity between the results was assessed according to Cochrane and I-squared indices. The prevalence of positive TST reactions was estimated using fixed and random effect models. Totally, 33 papers were entered into the meta-analysis reporting the TST results in 12693 people aged over 18. The prevalence (95% confidence intervals) of positive TST reactions in all groups, general population, health staff, medical students, household close contacts, patients with TB, immunocompromised patients, HIV/AIDS patients, and those with risky behaviors was 26.2% (19.6-32.8), 25.4% (4.8-46.1), 38.9% (27.4-50.9), 13.4% (9.9-16.7), 35.9% (16.4-55.5), 13.7% (8.4-18.9), 29.4% (21.2-37.7), and 14.6% (3.9-25.3), respectively. Our study showed great varieties of positive TST results among different Iranian subpopulations. Furthermore, the prevalence of latent TB infection among health professionals and family members of TB patients was considerably different from that of the other subgroup. Since TB control programs such as active case finding are routinely conducted among household close contacts and HIV/AIDS cases, other high-risk groups including health-care workers and immunocompromised patients should be taken into consideration in these preventive programs.

Estimating Tuberculin Skin Test Reactions among Children and Teenagers Who Received the Bacillus Calmette-Guerin Vaccination at Birth: A Meta-analysis

OBJECTIVES

Tuberculin skin reaction size is one indicator of bacillus Calmette-Guérin (BCG) vaccine efficacy and a way to diagnose latent infection. Several primary studies have examined this issue. Combining the results of these studies using a meta-analysis will provide reliable evidence regarding this indicator for policymakers. This study aimed to estimate the total frequency of different tuberculin skin test reactions among Iranian children and teenagers who received the BCG vaccination at birth.

METHODS

National and international databanks were searched using relevant keywords. After the search strategy was restricted and duplicates were excluded, the titles and abstracts of the remaining papers were screened. All included studies included healthy children who received the BCG vaccine without confirmed tuberculosis exposure. Heterogeneity of the results was assessed using the Cochrane test and I² index showed the random effects model as the best model for estimating the pooled results.

RESULTS

We combined the results of 14 primary studies including purified protein derivative reaction test measures of 26,281 Iranian children. The frequencies (95% confidence intervals) of the reactions were 8.5% (6.2-10.8) for patients with a reaction size ≥ 10 mm, 29.9% (22.3-37.4) for a reaction size of 5-9 mm, and 60% (48.9-71.1) for a reaction size < 5 mm.

CONCLUSION

Our study showed that large numbers of Iranian children and teens have no positive BCG vaccine reaction and a considerable number of children have been exposed to Mycobacterium tuberculosis.

The prevalence of latent tuberculosis infection in rural Jiangsu, China

OBJECTIVES

Diagnosis and interventional treatment of latent tuberculosis (TB) infection (LTBI) are important components in tuberculosis control. But systematic studies regarding the epidemic of LTBI are still rare in China. The objective of this study was to assess the prevalence and risk factors associated with LTBI based on the results of a domestic TB-specific gamma interferon (IFN-γ) release assay (TB-IGRA) in rural Jiangsu, China.

STUDY DESIGN

Cross-sectional study of subjects registered in eight villages in Jiangsu, China.

METHODS

This study was conducted in 2012 in eight villages. After recruitment, individuals with active TB or a history of TB were excluded. The TB-IGRA was performed for diagnosis of LTBI.

RESULTS

2169 of 2185 subjects met the requirement and were analysed in this study. 524 (24.3%) had a positive result, and positive rate gradually increased with age (P for trend <0.001). Multivariate analyses showed that increasing age, male gender and a history of TB exposure were risk factors associated with LTBI. Bacillus Calmette-Guérin (BCG) vaccination did not reduce the risk of TB infection in participants (aged ≥20 years).

CONCLUSIONS

The findings of this study demonstrate that the prevalence of LTBI in China might be overestimated by tuberculin skin test compared with IFN-γ release assay (IGRA). The degree of TB exposure is related to Mycobacterium tubercuium (MTB) infection, and BCG vaccination offers little protection against MTB infection in adults. The early and effective detection and treatment of active TB patients, and screening and intervention for LTBI patients with a high risk of developing active TB could be cost-effective methods for TB control in China.

The impact of diabetics and smoking on gender differences of smear positive pulmonary tuberculosis incidence

BACKGROUND

Several determinants are responsible for different incidences of smear positive pulmonary tuberculosis (TB). The main determinants are cigarette smoking and diabetes mellitus. The aim of this study is to determine the effect of these risk factors effect modifiers in TB/gender association.

METHODOLOGY

In this retrospective cohort, relative risk of gender in developing smear positive TB as well as its interaction with smoking and diabetes mellitus were investigated.

RESULTS

Of 1243 smear positive TB cases, 63.2% were male. Prevalences of diabetes mellitus among men and women TB cases were 9.2% and 22.9% respectively (p<0.001). Frequency of cigarette smoking among men was significantly higher than that in women (61.7% vs. 7.6% respectively, p<0.001). Male gender, increased the risk of developing smear positive TB as of 98% and 5% in smokers and non-smokers respectively (p=0.001), indicating an interaction between gender and smoking in the effect on TB. In addition, male gender increased the risk of TB as of 13% and 34% in patients with and without diabetes mellitus respectively (p=0.300) indicating no interaction between gender and diabetes mellitus on TB incidence.

CONCLUSION

Our study showed that cigarette smoking is a determinant factor for gender differences in TB incidence but diabetes mellitus does not affect the association between TB and gender.