What are the indications of active tuberculosis?

Active tuberculosis (TB) is characterized by specific clinical indicators. A positive Tuberculin Skin Test (TST) indicates exposure to the TB bacteria, but for an active infection to be confirmed, additional signs are necessary. One key aspect of active TB is that it often presents with a positive chest X-ray (CXR), which typically reveals abnormalities such as cavitary lesions or infiltrates consistent with active disease.

Moreover, individuals with active TB can be contagious, meaning they can spread the bacteria to others, especially when they are exhibiting respiratory symptoms such as a persistent cough, weight loss, fever, and night sweats. The combination of a positive TST, a positive CXR, and the potential for contagiousness highlights the severity of the infection and the need for immediate medical intervention.

The other options do not fulfill the criteria for active TB. For instance, having no signs or symptoms does not align with a diagnosis of active TB; similarly, a negative TST with a positive CXR is contradictory, as a negative TST suggests the absence of TB infection. A positive TST alone is insufficient to confirm active disease without accompanying clinical evidence. Thus, the comprehensive nature of option C makes it the correct choice, accurately reflecting the characteristics of active tuberculosis