Routine sputum culture is a laboratory test that looks for germs that cause infection. Sputum, sometimes referred to as phlegm, is a viscous mucus produced in your lungs. You may cough up sputum if you have an infection or a long-term condition that affects your lungs or airways. Sputum is made up of immune system cells that support your body's defences against bacteria, fungi and other foreign invaders in your lungs and airways. Sputum thickness aids in capturing the foreign object. It can then be coughed out thanks to the cilia (tiny hairs) in the airways, which push it out the mouth. AFB is Acid-fasting Bacillus, acid-fasting is the property of certain bacterial cells. The AFB Smear test is carried out when a person is suspected to have Tuberculosis. The tuberculosis infection is caused by the Mycobacterium tuberculosis AFB. The test is carried out by taking the sample from the patient and is the fastest yet effective tests available to detect tuberculosis. The negative test results means that the infection is not present in the patient. A positive AFB test result indicates the presence of mycobacteria in the sample. The negative sample may contain infection and is therefore the sample is still allowed to grow in the culture.