Pulmonary Tuberculosis III

Tuberculosis can be classified into the following six categories based on disease progression:

Class zero indicates no known tuberculosis exposure with a negative reaction to the tuberculin skin test.

Class one suggests exposure to tuberculosis, but no evidence of infection, and the tuberculin skin test is negative.

Class two represents latent tuberculosis infection, with a positive tuberculin skin test without clinical, bacteriological, or radiographic evidence of tuberculosis disease.

Class three exhibits clinically active tuberculosis, displaying a positive tuberculin skin test with current tuberculosis disease based on clinical, bacteriological, or radiographic evidence.

Class four shows clinically non-active tuberculosis but has a history of prior tuberculosis episodes or abnormal yet stable radiographic findings in the absence of current symptoms. However, the tuberculin skin test may exhibit a positive reaction.

Class 5 indicates suspected tuberculosis, with pending laboratory tests.

Further classification depends on the infection's location. Pulmonary tuberculosis affects lung tissue, while extrapulmonary tuberculosis can spread beyond the lungs to several other areas, like joints and the nervous system.