If pulmonary tuberculosis is suspected, the sputum must be examined. This is to detect the pathogen. The sputum should be coughed up from the deeper parts of the lungs, as saliva from the mouth is not suitable. This is collected in a medical container and sent to the laboratory immediately, as older samples, for example from the previous day, are unusable. If no sputum can be released spontaneously, inhaling saline solution can help to loosen the mucus in the lungs.

If the sputum contains a lot of tuberculosis bacteria, these can be made visible under the microscope using special staining. Using molecular genetic tests, the laboratory can quickly determine whether it is tuberculosis or other non-infectious bacteria - so-called non-tuberculous mycobacteria. In order to detect even the smallest amounts of tuberculosis bacteria and to determine other characteristics such as resistance of the bacteria, the samples are cultivated in the laboratory and subjected to certain tests. This process is known as culture. The results of the cultural examination can take several weeks, as tuberculosis bacteria grow very slowly. However, the microscopic and molecular genetic results are usually sufficient to start treatment.

If tuberculosis bacteria can be detected in the laboratory from the sputum or other examinations of the pulmonary tract, an infectious form of tuberculosis is present. During treatment, the sputum is therefore examined regularly to check the success of the therapy. As soon as the laboratory no longer detects any bacteria, the disease is generally no longer considered contagious. The final assessment of a possible contagiousness is decided by your doctors together with the public health department.