A negative Mycobacterium tuberculosis test is a test that detects a specimen with a Mycobacterium tuberculosis DNA content of <500copies/ml, but on the other hand, a negative Mycobacterium tuberculosis test does not necessarily mean that the patient is normal, because he or she must show symptoms of tuberculosis, which is why the doctor sent him or her to the testing center for the test. Because the content of Mycobacterium tuberculosis in the patient's body is relatively low and does not reach the lower limit of detection of the PCR instrument, or the replication of Mycobacterium tuberculosis genes in the early stage of infection has not reached a certain amount, not reaching 500copies/ml, not detected, which is now medically known as the window period. In this case, the patient is advised to observe further, or review, according to clinical symptoms.