Laboratory diagnosis of tuberculosis can be done in three ways: first, you see the bug (microscopy); second, you grow the bug (culture); and finally you multiply the bug (PCR). Micro-bacterium Tuberculosis test is performed on a sample of sputum to measure the concentration of TB bacilli in the sputum. It is performed to confirm the symptoms of Tuberculosis and also during and after the treatment of Tuberculosis. PCR stands for Polymerase Chain Reaction. A PCR test is useful in detecting complex organisms in the peripheral blood.