The complexity of diagnosing latent tuberculosis infection in older adults in long-term care facilities

Tuberculin skin test and predictive host factors for false-negative results in patients with pulmonary and extrapulmonary tuberculosis

INTRODUCTION

Tuberculin skin test (TST) has been the standard test for screening for Mycobacterium tuberculosis infection for decades. Identifying persons with latent tuberculosis infection (LTBI) is crucial, as they constitute a reservoir that sustains the global tuberculosis (TB) epidemic. However, different factors, such as HIV infection, can lower the sensitivity of the test.

OBJECTIVES

The aim of this study was to determine the TST sensitivity in active TB patients and to ascertain risk factors that could be associated with false-negative results.

METHODS

Retrospective cohort study of all active TB notifications with a TST result (n = 8833), from 2008 to 2015. TST results were interpreted using a 5 mm and 10 mm cutoff. Bivariate and multivariate logistic regression analysis were used to evaluate the association of sociodemographic and clinical factors with false-negative TST results and to develop predictive risk models.

RESULTS

TST presented an overall sensitivity of 63.8% (5 mm) and 56.1% (10 mm). HIV infection was the risk factor with the strongest association with false-negative results (aOR 4.65-5 mm; aOR 5.05-10 mm). Other factors such as chronic renal failure (CRF) (aOR 1.55-5 mm; aOR 1.73-10 mm), alcohol abuse (aOR 1.52-5 mm; aOR 1.31-10 mm), drug abuse (aOR 1.90-5 mm; aOR 1.76-10 mm) or age ≥65 years (OR 1.69-5 mm and 10 mm) were also associated with a probability of false-negative results.

CONCLUSION

These results highlight the importance of knowing which factors influence TST results, such as HIV status, substance abuse or age, thus improving its usefulness as a screening method for LTBI.

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

BACKGROUND/PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

There was a high prevalence of LTBI among older adults in LTCFs in Taiwan. Independent ambulation was the only independent predictor of LTBI.

Enduring Challenge of Latent Tuberculosis in Older Nursing Home Residents: A Brief Review

Tuberculosis (TB) kills almost 4,000 people a day and is competing with human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) as the most deadly infectious disease in the world. The gold standards of detection and management of latent tuberculosis infection (LTBI) have not been successful in complete eradication of the disease. Current screening modalities of TB include tuberculin skin testing (TST) and/or interferon-γ release assay (IGRA). However, these screening tests have been heavily studied in healthy populations but not in the elderly who are more likely to have multiple risk factors for progression to active TB from LTBI. The largest population that is harboring LTBI is the elderly, specifically those residing in nursing homes. Yet, unfortunately, guidelines for standards of detection and treatment for this specific group are lacking. In this review, we look at TST versus IGRA screening for LTBI in the elderly living in nursing homes. We review a cross-sectional study done at Staten Island University Hospital, and several other assessments of the sensitivity and accuracy of both screening tools. Furthermore, this review looks at the appropriateness of current LTBI treatment and prophylaxis in elderly patients residing in close quarters. The reviews point to the superiority of IGRA testing in the elderly for screening LTBI. The IGRA has been shown to be more sensitive to the detection of LTBI than TST. Additionally, medical complexities that the elderly population possesses may present challenges and resistance to standard treatments of LTBI. It is recommended via the literature that the addition of vitamin D, or alternative therapies (e.g. rifampin) could produce better outcomes for elderly patients with LTBI than the current 9 months of isoniazid (INH). As the older adults represent the fastest growing segment of our population and the largest LTBI reservoir in the USA, revisiting screening and treatment of LTBI in the elderly living in nursing homes may prove to lead to a path of TB eradication once and for all.

Comparative proteomic profiles reveal characteristic Mycobacterium tuberculosis proteins induced by cholesterol during dormancy conditions

Cholesterol has been reported to play an important role during Mycobacterium tuberculosis infection and during its dormant state inside the host. We present the determination of proteomic profiles of M. tuberculosis H37Rv in the presence of cholesterol as the sole carbon source under exponential growth and in two in vitro dormancy phases (NRP1 and NRP2). Using 2D-PAGE, we detected that M. tuberculosis expressed a high diversity of proteins in both exponential and non-replicative phases. We also found that cholesterol was involved in the overexpression of some proteins related to sulfur metabolism (CysA2), electron transport (FixB), cell wall synthesis (Ald), iron storage (BfrB), protein synthesis (Tig and EF-Tu) and dormancy maintenance (HspX and TB 31.7). According to our results we propose that proteins Ald, BfrB, FadA5 and TB31.7 are likely to play a fundamental role during in vitro dormancy of M. tuberculosis in the presence of cholesterol, helping to counteract its intracellular hostile microenvironment.

Tuberculosis in Enclosed Populations

Transmission of tuberculosis (TB) is most effective in close contact indoor environments in various congregate settings including health care facilities, homeless shelters, correctional facilities, long-term care facilities, as well as community settings such as homes, schools, workplaces, and various modes of transportation. Outbreaks are fueled by numerous factors including the HIV epidemic, ease of global travel, unstable socio-economic and/or political situations, and lapses in response to potentially infectious patients. Organized approaches to TB control include an appropriate index of suspicion, identification and isolation of contagious patients in appropriate facilities, use of environmental controls, and personal protective equipment in accordance to national and international published guidelines. These all require tailoring to the various settings where TB is encountered using a determination of risk. Concerted efforts at the local, regional, national, and international levels at identifying patients with active disease, enforcing completion of treatment, and testing and fully treating patients with latent TB infection are paramount in reducing TB burden and continued transmission.

Using genotyping to delineate tuberculosis transmission in long-term care facilities: single facility 4-year experience

Background

Residents in long-term care facilities (LTCFs) are vulnerable to tuberculosis (TB) transmission; however, to delineate possible routes of TB transmission in LTCFs is difficult. This study aimed to address the use of regular genotyping surveillance to delineate TB transmission in LTCFs.

Methods

All of Mycobacterium tuberculosis isolates in the reported 620-bed LTCF between July 2011 and August 2015 were genotyped, and we retrospectively compared epidemiological data and genotyping results.

Results

A total of 42 subjects were diagnosed with culture-positive pulmonary TB infection during the 4-year period. Their median age was 76.5 years, and 64.3% (27/42) of them were male. Genotyping identified 5 clustered TB infections involving 76.2% (32/42) of all TB subjects. In a multivariate logistic regression model adjusted for age, sex, chronic obstructive pulmonary disease, and body mass index, subjects with clustered TB infection were less likely to be Activities of Daily Living (ADL)-dependence (adjOR 0.073, 95% CI 0.007–0.758) when compared with subjects having individual TB infections. Prolonged surveillance is essential given that the median interval to diagnose secondary subjects was 673 days. Finally, only 63.0% (17/27) of the 27 secondary TB subjects in this study had contact history with index subject in the same ward.

Conclusions

In conclusion, possible routes of TB transmission in a complex TB outbreak at LTCFs might be delineated by routine genotyping surveillance and regular health check-up.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2526-2) contains supplementary material, which is available to authorized users.

B cell responses in older adults with latent tuberculosis: Considerations for vaccine development

Reactivation of latent tuberculosis (LTBI) is more common among the aging population and may contribute to increased transmission in long-term health care facilities. Difficulties in detecting LTBI due to potential blunting of the tuberculin skin test (TST), and the lowered ability of the elderly to tolerate the course of antibiotics, underscore the need for an effective vaccine. Immuno-senescence reduces the capacity of vaccines to induce sufficient levels of protective immunity against many pathogens, further increasing the susceptibility of the elderly to infectious diseases. We sought to evaluate the response of B cells to Mycobacterium tuberculosis (Mtb) in residents of long-term care facilities to determine the feasibility of using a vaccine to control infection and transmission from reactivated LTBI. Our results demonstrate that although B cell responses were higher in subjects with LTBI, Mtb antigens could stimulate B cell activation and differentiation in vitro in TST negative subjects. B cells from elderly subjects expressed high basal levels of Toll-like receptor (TLR)2 and TLR4 and responded strongly to Mtb ligands with some activation pathways dependent on TLR2. B cells derived from blood, tonsil and spleen from younger subjects responded similarly and to the same magnitude. These results suggest that B cell responses are robust in the elderly and modifications to a TB vaccine, such as TLR2 ligand-based adjuvants, may help increase immune responses to a protective level.

Does tuberculosis threaten our ageing populations?

Background

The global population is ageing quickly and our understanding of age-related changes in the immune system suggest that the elderly will have less immunological protection from active tuberculosis (TB).

Discussion

Ongoing global surveillance of TB notifications shows increasing age of patients with active TB. This effect of age is compounded by changes to clinical manifestations of disease, confounding of diagnostic tests and increased rates of adverse reactions to antimicrobial treatment of TB. Future epidemiological surveillance, development of diagnostic tests and trials of treatment shortening should all include a focus on ageing people.

Summary

More detailed surveillance of TB notifications in elderly people should be undertaken and carefully evaluated. Risk stratification will help target care for those in greatest need, particularly those with comorbidities or on immunosuppressive therapies. Novel diagnostics and treatment regimes should be designed specifically to be used in this cohort.