OVERVIEW
WHAT IS ASPIRATION FLUID FOR AFB SMEAR TEST?
The investigation of pleural effusion of unknown cause may include analysis of pleural aspirate for the presence of acid-fast bacilli (AFB) by smear. Pleural effusion is the accumulation of fluid in the pleural space, an area between the lung tissues and the chest wall.
Mycobacteria are called acid-fast bacilli because they are a group of rod-shaped bacteria (bacilli) that can be seen under a microscope following a staining procedure where the bacteria retain the color of the stain after an acid wash. AFB laboratory tests identify the infection by detecting the bacteria in a person's sample.
WHAT DOES THE TEST MEASURE?
AFB smear testing may be used to detect different types of acid-fast bacilli, but it is most commonly used to identify an active tuberculosis infection. AFB smear is a microscopic examination of a person's sputum, that is stained to detect acid-fast bacteria. AFB smear results must be compared with AFB culture.
How is the test performed?
Sputum is the most commonly collected sample. Sputum is a thick mucus that is coughed up from the lungs. If a person is unable to produce sputum, a healthcare practitioner may collect respiratory samples using a procedure known as bronchoscopy. The practitioner will insert a tube into the bronchi and smaller bronchioles and aspirate fluid samples for testing.
Is any test preparation needed?
No test preparation is needed, except to rinse the mouth with saline water before collecting the sample.
What are the signs and symptoms of active tuberculosis?
Signs and symptoms of active tuberculosis include
- Coughing that lasts 3 or more weeks
- Cough with blood
- Chest pain
- Pain with breathing or coughing
How is Mycobacterium spread?
Mycobacterium tuberculosis is carried in airborne particles. TB is spread from person to person through the air
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 smear confirms the presence of Mycobacterium
A Positive result several weeks after the treatment indicates that the treatment
is not effective and needs to be changed.