Acid Fast Bacilli (AFB) are those that are resistant to the action of acid. This characteristic of theirs is used to detect their presence in the AFB test. Mycobacteria are the most common acid fast bacilli. Mycobacteria are of two species – Mycobacterium leprae, that cause leprosy, and Mycobacterium tuberculosis, that cause tuberculosis. Tuberculosis is usually pulmonary in nature. However, apart from the lungs, it is sometimes found in the bones, brain and other organs. Pulmonary tuberculosis is an air-borne infection, spread by coughing and sneezing of infected individuals. Tuberculosis is prevalent in developing countries such as India. AFB test is used to diagnose TB. Timely diagnosis of the disease can prevent spreading of the infection.

The test is used to detect mycobacterial infections. It is ordered when these symptoms of pulmonary tuberculosis are observed:

The test shows presence of Tuberculosis-causing bacteria in the sputum tested. However, if positive in one sample, it is insufficient to make a diagnosis and a minimum of 3 tests samples are required to be performed to show a true result.If any 2 of 3 or if 3 out of 3 are positive, it indicates a pulmonary tuberculosis infection in your lungs, since a sputum sample is specific for lung TB only.

When the test is positive (2 of 3 tests or 3 out of 3) for 2 or more samples, it indicates and infection with Tuberculosis. This requires a detailed check up with other tests as well and a good follow up with a Pulmonologist for the management and further treatment of the infection. Depending on the case, it is important to check liver function and kidney function prior to starting medication, as well as  other medical history. In newly diagnosed cases, a course of ATT (Anti-tuberculosis treatment) is prescribed comprising of 4-5 drugs at times. This is slowly tapered down and the total duration of treatment can last anywhere from 3-9 months.

Is it possible to have Mycobacteria and not be infected with tuberculosis?
Yes. Mycobacteria can be present in the body but not in enough quantity to cause an infection. Such latent infections are present in many people, 90% of whom will not progress to an infectious stage. Only if their immunity decreases, can the Mycobacteria multiply. Also, people with previous infections who have been cured may have latent bacteria present in their tissues.

What is the treatment for tuberculosis?
A six to nine-month treatment of a combination of drugs is used to treat tuberculosis. Usually, rifampicin, isoniazid, pyrazinamide and ethambutol are the drugs of choice. Patients need to take extreme care to take drugs at the correct dosages and time, as failure to do so can lead to drug resistance. Along with drugs, a high protein diet and mild exposure to sunlight is also recommended during convalescence. 

What is drug resistant tuberculosis?
Resistance to the first line of drugs (rifampicin and isoniazid) is called multi drug resistant tuberculosis (MDR-TB). MDR-TB patients are treated with second line drugs (amikacin, kanamycin, or capreomycin). Resistance to second line drugs as well, is termed as extremely drug resistant tuberculosis (XDR-TB). 

Adenosine Deaminase (ADA)

AFB Culture (automated)

AFB Culture (ZN staining)

AFB Culture (LJ method)

Sputum Culture & Sensitivity

Sputum Gram Stain & Culture