Smear AFB

AFB denotes Acid-fast bacteria, also called acid-fast bacilli. These are a group of bacteria sharing the property of acid fastness, that is the physical ability to resist decolorization by acids during staining procedures. This unique feature serves as a distinguishing ability in classifying and detecting acid-fast bacteria like Mycobacteria.

Direct microscopic examination plays a key role in the diagnosis and monitoring of treatment in TB-infected patients. The presence of AFB in microscopically examined smears provides bacteriological evidence of Mycobacterium, the bacterium responsible for Tuberculosis in a clinical specimen. The test provides a count of bacilli in accordance with India’s National Tuberculosis Elimination Programme, allowing bacterial load in the sample to be estimated and further tests to be guided.

A negative AFB smear result does not rule out TB infection. The test should be repeated with a new sample after a specific period of time as suggested by the doctor.

Why Get Tested with Smear AFB?
The smear AFB test is a microscopic technique used for the detection of acid-fast bacteria like Mycobacterium. It is commonly used for the detection of active Tuberculosis infection as well as for monitoring the efficiency of treatment.

When to get tested with the Smear AFB test?
Smear AFB test is recommended if the individual is suspected of being infected with Mycobacteria or develops symptoms of Tuberculosis like cough for more than 3 weeks with blood or sputum, chest pain, weakness, fatigue, loss of appetite, chills, fever, sweating at night or weight loss.

What sample is required and what preparation is needed for this test?

A number of samples including body fluids, sputum, bronchial alveolar lavage, cerebrospinal fluid (CSF), pus, tissue, biopsies, lymph nodes, abscess, urine can be used for performing this test. There is no special preparation required before getting this test.

What are the types of drug-resistant TB?
Drug-resistant tuberculosis infection, caused by drug-resistant Mycobacterium tuberculosis (MTB) bacterium is divided into the following categories

• Multidrug-resistant or MDR-TB: MDR-TB is the TB infection caused by MTB that is resistant to the most potent drugs used in TB treatment – isoniazid and rifampin.
• Extensively drug-resistant or XDR-TB: XDR-TB is the TB infection caused by MTB that is resistant to most commonly used drugs used in TB treatment like isoniazid and rifampin, plus any fluoroquinolone as well as at least one of the three injectable second-line drugs (amikacin, kanamycin, and capreomycin).

Is there any vaccine for Tuberculosis? Can TB be cured?
Bacille Calmette-Guérin (BCG) is the vaccine available for prevention of TB infection. TB is a preventable and curable disease. Active infections can be treated with a 6-month course of antimicrobial drugs.

What is LTBI?
LTBI stands for Latent Tuberculosis Infection and is the stage where an individual has TB bacteria in the body but is not sick and cannot spread the infection. However, individuals with LTBI require treatment of latent infection to prevent the disease.