Hello, I understand the confusion that this situation can create, although it is not uncommon in TB. A skin test cannot reliably diagnose an active TB infection and thus a negative test does not rule out tuberculosis. Sputum can often diagnose tuberculosis, but when sputum samples are insufficient, bronchoscopic samples may be collected by a physician. These samples are far more accurate and reliable than simple sputum samples. A positive culture for TB from a bronchoscopic sample is very reliable and indicates infection with tuberculosis. The only important caveat is that the TB culture can sometimes pick up other bacteria as well. The AFB (Acid fast bacilli) culture can start growing bacteria that look like TB but are different bacteria (nontuberculous Mycobacteria). You should ask the doctor if the result so far is positive for Acid Fast Bacilli or for Tuberculosis. It takes a little bit of time to be able to identify the organism is true TB after the initial detection of Acid Fast Bacilli. I hope this clears things up a little bit.