PCR is a method that detects small amounts and parts of the organism's genetic material. It can be used for the following purposes:
To detect Mycobacteria (the organisms that cause tuberculosis);
To distinguish between "Mycobacterium tuberculosis", which causes most cases of tuberculosis and other species of Mycobacteria;
To identify strains of "Mycobacterium tuberculosis" that are resistant to the drugs that are usually used to treat tuberculosis; and
To look at strains of "Mycobacterium tuberculosis" from a group of people who have tuberculosis to see if they have the same strain. For example, this test can be used to indicate if the organism has spread between people in this group or if they have contracted tuberculosis from other people and have an unrelated strain.