TB/AFB PCR - Test, Procedure & Cost

AFB tests are used to diagnose tuberculosis (TB) infection and scrutinize treatment cogency. They also help to diagnose other types of AFB(Acid fast bacillus) infections. One example of AFB infection is Leprosy, a treatable disease that affects the nerves, eyes, and skin of the human body. The most common AFB are of a type called mycobacteria.

Mycobacterium tuberculosis complex is the most common species of mycobacteria, and it is the most infectious infection.

Since TB is spread by air from coughing and sneezing, it is a public health risk. It can spread in confined populations, such as correctional facilities, nursing homes, and schools. Those who are very young, elderly, or have diseases and conditions such as AIDS that can damage their immune systems are especially likely to become infected.

When To Get Tested?

You need to get tested if you have symptoms, such as a pro-long-lasting cough, weight loss, fever, chills, and weakness, or if your doctor suspects that you have a TB and desires to monitor the effectiveness of TB treatment.

What type of sample is required?

You are required to provide three separate sputa (saliva) samples from early mornings on different days. 

Depending on the symptoms the patient shows, urine, cerebral spinal fluid (CSF), other body fluids, and samples of tissue may be biopsied and used to help identify an infection.

What is Tested?

The test examines the presence of bacteria called acid-fast bacilli (AFB). These are rod-shaped bacteria that can be seen and counted under the microscope when a specially stained sample is on a glass slide; it is called an AFB smear.

What is the importance of this test?

• These are used to determine whether the TB is only in the lungs or has spread to organs outside the lungs.
• They also help to identify M. tuberculosis and find out the most effective antimicrobial medicine to treat the infection.  
• If the bacteria are resistant to more than one of the common drugs used for therapy, the organisms are called 'multi-drug resistant' TB (MDR TB). If the bacteria are resistant to multiple first and second lines of treatment, they are called 'extensively drug-resistant tuberculosis (XDR TB).

Interpretation of Results

• Positive AFB smears may indicate a mycobacterial infection.
• A positive AFB smear or culture several weeks after drug treatment has started may mean that your treatment is not effective and needs to be changed. It also means that you are still likely to be infectious and can pass the mycobacteria to others through coughing or sneezing.
• A negative AFB smear or culture means that you do not have an AFB infection or that the mycobacteria were not present in that particular specimen (which is why multiple samples are often collected).