Understanding Tuberculosis Stages: A Complete Guide

What stage of TB are individuals in if they consistently test positive on TB skin screenings but are asymptomatic and not infectious?

A) Primary infection
B) Latent TB
C) Secondary TB
D) Active pulmonary TB

Final answer:

Individuals with a positive TB skin test but no symptoms are in the Latent TB stage, indicating exposure to TB bacteria but not active infection. The Mantoux tuberculin skin test detects an immune response to TB but can give false positives due to the BCG vaccine, which complicates interpretation in areas where the vaccine is used.

Explanation:

Individuals who consistently test positive on TB skin screening tests but are asymptomatic and not infectious are most likely in the stage of Latent TB. This stage is characterized by the presence of Mycobacterium tuberculosis in the body but with the bacteria being inactive. These individuals do not show symptoms and cannot spread the disease to others. In the latent TB stage, the immune system walls off the infection, as indicated by the formation of tubercles mentioned in the provided Figure 22.13. A positive reaction to the tuberculin skin test, such as induration, means that the individual has been exposed to the TB bacteria and has a cellular immune response to it, but it does not necessarily indicate active infection.

The Mantoux tuberculin skin test is used to determine whether a person has been exposed to the bacteria. However, the BCG vaccine, which is not used in the United States, can cause false-positive results because it also elicits an immune response that the test can detect. In areas where the BCG vaccine is common, interpreting the results of the tuberculin skin test can be complex, as a positive result could be due to prior vaccination.