Sputum examination requires the use of more than 2 ml of sputum each time, because only by ensuring that the amount of sputum examined is at least 2 ml, it is possible to ensure the amount needed in the test. The sputum test can detect suspected pathogens, such as bacteria, viruses and Mycobacterium tuberculosis, and can clarify pathogenic infections and increase the rate of positive sputum tests. In clinical practice, the diagnosis of pulmonary tuberculosis caused by Mycobacterium tuberculosis infection and the assessment of the efficacy of treatment can be initially obtained by sputum examination. If the amount of sputum obtained is too small, the accuracy of the results may be affected and the positive rate of sputum testing may be reduced, and even a false negative rate may occur, so sputum testing requires at least 2 ml of sputum.