OVERVIEW
WHAT IS AFB C/S (SPUTUM) LAB TEST?
The AFB culture test is performed on a sputum sample. The acid-fast Bacilli culture test is one of the TB culture and sensitivity tests where the Mycobacterial infection is diagnosed on the blood smear. Tuberculosis is a lung infection caused by Mycobacterium Tuberculosis. Mycobacterium is called acid-fast bacilli because after an acid wash the bacteria retain the color of the stain. They can then be seen under the microscope.
During a bacterial culture test, an examination is done by growing the bacteria on different substances. The sample is obtained from sputum, blood, urine, or other parts of the body.
WHAT DOES THE TEST MEASURES?
AFB cultures help in the diagnosis of active Mycobacterium tuberculosis infections as well as infections due to nontuberculous mycobacteria (bacteria found in soils and water. AFB culture is more sensitive than an AFB smear, positive results may take days to several weeks, while negative culture results (no mycobacterial growth) can take up to 6 to 8 weeks to confirm.
The AFB culture's initial report comes after three weeks, while the final test result is reported after 7 weeks.
Q1. How is the test performed?
Mycobacterium tuberculosis infects the lungs, sputum is the most commonly collected sample. An early morning, deep cough specimen is collected in a container provided by the laboratory.
Q2. Is there any risk associated with this test?
No risk is associated with the test
Q3. What is the difference between tuberculosis and pneumonia?
Tuberculosis is a contagious bacterial disease while pneumonia is not contagious.
Q4. What is the difference between a smear and a culture test?
A smear is a microscopic examination of bacteria on a slide whereas, a culture test is the growth of bacteria on different substances.
INTERPRETATION OF THE RESULT:
- A negative result before any treatment means that the person tested does not have an active AFB infection or that mycobacteria were not present in that sample.
- A negative result several weeks after the treatment indicates that the TB infection is responding to the treatment, and the person is no longer infectious.
- A positive AFB culture confirms the presence of Mycobacterium Tuberculosis
- A Positive result several weeks after the treatment indicates that the treatment the regimen is not effective and needs to be changed.