TB - Culture & TB Gold & Genexpert Test
Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis bacteria and can affect any part of the body, mostly the lungs. Tuberculosis can spread through coughing or sneezing small droplets of bacteria into the air, which is then inhaled by a susceptible person.
Testing for TB, usually involves checking your blood, and sputum samples to see if you are infected with the A TB culture and tests help to know if you have an infection; with early detection, you can receive early treatment. Thus, getting your TB – culture done is recommended to prevent various TB- related complications
Symptoms of TB
The common symptoms of TB include:
Cough for more than 3 weeks
Coughing of blood or sputum
Fever
Weight loss
Fatigue
Night sweats
Headache
Joint pains
Chills
Loss of appetite
Difficulty in breathing
Chest pain
Types of Test to Diagnose TB
The following tests can be performed to identify TB:
TB Skin Test (TST):
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It is also called a “Mantoux test or tuberculin skin test”. During TST, a tiny amount of tuberculin (protein) is injected under the skin of the forearm. After 48 to 72 hours, following the injection, the skin will be examined for any reaction. It is preferred for children under the age of 5 years.
Blood Test
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It is also called an “Interferon-gamma release assay “(IGRA) or “QuantiFERON” (commercial name) –TB Gold plus. It determines the presence of TB bacteria in your blood. During this test, a healthcare provider will draw blood and send the collected sample to the laboratory for analysis. It is preferred for individuals who have received the TB vaccine
Sputum Test
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The mucus that comes up when you cough is sputum. This test is performed to determine the various TB bacterium strains, including antibiotic-resistant variants in your sputum. It is the accurate way of testing for active TB. Both smear and culture tests will be performed on your sputum sample
Gene-Xpert:
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A CBNAAT (cartridge-based nucleic acid amplification test) called Gene-Xpert is a commonly used diagnostic tool for tuberculosis. In circumstances where a direct smear test is negative, this test can quickly diagnose both the presence of tuberculosis and the presence of drug resistance. A sputum sample is collected to perform this test
Who should get screened for TB?
TB Culture is recommended for individuals who are at high risk of developing tuberculosis. The following factors can increase the risk
Smoking
HIV infection (the virus that causes AIDS)
Drugs and alcohol consumption
Diabetes mellitus
Severe kidney disease
Low body weight
History of organ transplantation
Preparation for test
No special preparation is required for this test.
Interpretation of the Test Results
TB skin test Interpretation
The result of the skin test depends on the size of the raised area of the skin in the region of injection. The result may be positive or negative.
Positive TB Skin test: It means that your body was infected with mycobacterium bacterial species. Further tests may be required to determine whether you have a latent TB infection or recent TB infection.
Negative TB Skin test: It means that your body was not infected with mycobacterium bacterial species and you are not having Latent TB or a recent TB infection.
TB Blood test Interpretation
The result may come as positive or negative.
Positive TB blood test: It means that your blood has been infected with TB bacteria. Further tests may be required to determine whether you have a latent TB infection or a recent TB infection.
Negative TB blood test: It means that your blood is not infected with TB bacteria and you are not having Latent TB or a recent TB infection.
TB Sputum test Interpretation
Positive TB sputum result: If the results of your sputum test were positive, it means that you have either active TB or another mycobacterial infection.
Negative TB sputum result: If the results of your sputum test were negative, it means that you most likely don’t have active TB or other mycobacterial infections.
Gene-Xpert Interpretation
As compared to smear microscopy and culture, Genexpert is found to be a quick test for the diagnosis of TB and rifampicin resistance. A positive smear and a negative Genexpert test increase suspicion of nontuberculous mycobacteria (NTM) infection
FAQs
What can I do to stop TB from spreading to other people?
If you are infected, take the following precautions at home to safeguard others in your vicinity.
As directed, take your medications without fail. This is very crucial. When you laugh, sneeze, or cough, make sure to cover your mouth with a tissue. Safely dispose off the tissue by placing it in a zippered bag. Avoid close contact with anyone and isolate yourself from others. For the first several weeks, sleep in a bedroom apart from other family members
What should I do if I have TB and am pregnant?
When TB is suspected in a pregnant woman, treatment should be started. Although coping with TB during pregnancy is difficult, getting the right care is essential for the mother's and the unborn child's health. A pregnant woman and her foetus are at more risk from untreated TB disease than from its treatment
How long should I wait to get my TB sputum test result?
Results from a typical sputum culture can be obtained in 1 to 8 weeks. Within 24 hours, a quick sputum test can determine if someone has TB. However, when a person is suspected of having TB, it should be confirmed by performing sputum culture results
What is the normal range for the Quantiferon TB Gold Test?
A blood sample is subjected to the Quantiferon TB Gold Test, a Wasserman test for identifying Mycobacterium tuberculosis infection. The Quantiferon TB Gold Test has upper and lower limits of 10 mcg/L and 1 mcg/L, respectively, hence a result between 9 and 10 mcg/L is regarded as normal
If I feel better while taking TB medication, can I stop taking it?
It is important to complete your TB medication course in order to recover from TB. When medication is interrupted or dosages are missed, the TB bacterium has a chance to evolve and become drug-resistant. Drug-resistant strains can be potentially fatal and are more challenging to treat
Related tests
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