What is the purpose of a sputum culture in diagnosing tuberculosis?

A sputum culture is primarily used to identify the presence of the bacteria that cause tuberculosis. This process involves collecting a sputum sample from a patient, which is then cultured in a laboratory to check for the Mycobacterium tuberculosis bacteria. The culture helps confirm a diagnosis of tuberculosis by providing evidence of active infection, as it allows for the growth of the organism in a controlled environment.

In contrast to the other options, measuring the immune response or assessing lung capacity does not directly contribute to diagnosing tuberculosis. While evaluating treatment efficacy is an important aspect of tuberculosis management, it is not the primary purpose of performing a sputum culture. The main goal of the sputum culture is to definitively identify the presence of the tuberculosis bacteria, which is crucial for initiating appropriate treatment and control measures.