Tuberculosis in special populations.

The susceptibility to infection, the pathogenesis and the clinical manifestations of tuberculosis (TB) depend on the immunological status of the host. Immunological status is largely determined by age and comorbidities, but is also affected by other less well known factors. In Spain, most incidental cases of TB arise from the reactivation of remotely acquired latent infections and are favored by the aging of the population and the use of aggressive immunosuppressive therapies. The diagnosis and management of TB in these circumstances is often challenging. On the one hand, the atypical presentation with extrapulmonary involvement may delay diagnosis, and on the other, the toxicity and interactions of the antituberculous drugs frequently make treatment difficult. Immigration from resource-poor, high incidence TB countries, where the social and economic conditions are often suboptimal, adds a new challenge to the control of the disease in Spain. This chapter summarizes our current knowledge of epidemiological, clinical and treatment aspects of TB in particularly susceptible populations.

Diagnosis of tuberculosis infection using interferon-γ-based assays.

Interferon-γ-based assays, collectively known as IFN-γ release assays (IGRAs), have emerged as a reliable alternative to the old tuberculin skin test (TST) for the immunodiagnosis of tuberculosis (TB) infection. The 2 commercially available tests, the enzyme-linked immunosorbent assay (ELISA), QuantiFERON-TB Gold Intube (QFT-IT), and the enzyme-linked immunospot assay (ELISPOT), T-SPOT.TB, are more accurate than TST for the diagnosis of TB, since they are highly specific and correlate better with the existence of risk factors for the infection. According to the available data, T-SPOT.TB obtains a higher number of positive results than QFT-IT, while its specificity seems to be lower. Although the sensitivity of the IFN-γ -based assays may be impaired to some extent by cellular immunosuppression and extreme ages of life, they perform better than TST in these situations. Data from longitudinal studies suggest that IFN-γ-based tests are better predictors of subsequent development of active TB than TST; however this prognostic value has not been consistently demonstrated. This review focuses on the clinical use of the IFN-γ -based tests in different risk TB groups, and notes the main limitations and areas for future development.

Tuberculosis in special populations

La susceptibilidad a la infección, patogenia y manifestaciones clínicas de la tuberculosis (TB) dependen dela situación inmunológica del hospedador, lo cual, a su vez, está determinado en gran medida por la edad ylas comorbilidades, pero también por otros factores no bien conocidos. La mayor parte de casos nuevos deTB en España tiene su origen en la reactivación de una infección remota latente, y es favorecida por el envejecimientoy las terapias inmunosupresoras agresivas. A menudo, el diagnóstico y tratamiento de la TB eneste contexto representan un reto. Las presentaciones atípicas, con afectación extrapulmonar, pueden retrasarel diagnóstico, pero además la toxicidad y las interacciones de los fármacos antituberculosos, a menudo,dificultan el tratamiento. La inmigración de países en vías de desarrollo y alta incidencia de TB, frecuentementecon condiciones sociales y económicas desfavorables, añade un nuevo reto al control de laenfermedad en España. En este capítulo se resume el conocimiento actual acerca de los aspectos epidemiológicos,clínicos y terapéuticos de la TB en poblaciones especialmente susceptibles (AU)

The susceptibility to infection, the pathogenesis and the clinical manifestations of tuberculosis (TB) depend on the immunological status of the host. Immunological status is largely determined by age and comorbidities, but is also affected by other less well known factors. In Spain, most incidental cases of TB arise from the reactivation of remotely acquired latent infections and are favored by the aging of the population and the use of aggressive immunosuppressive therapies. The diagnosis and management of TB in these circumstances is often challenging. On the one hand, the atypical presentation with extrapulmonary involvement may delay diagnosis, and on the other, the toxicity and interactions of the antituberculous drugs frequently make treatment difficult. Immigration from resource-poor, high incidence TB countries, where the social and economic conditions are often suboptimal, adds a new challenge to the control of the disease in Spain. This chapter summarizes our current knowledge of epidemiological, clinical and treatment aspects of TB in particularly susceptible populations (AU)