TB Confirmation Panel -GeneXpert, Smear & Culture Test
TB Confirmation Panel -GeneXpert, Smear & Culture Test
Tuberculosis is a communicable disease, which a person contracts when they inhale air droplets released by an infected person. This is caused by a bacteria called Mycobacterium tuberculosis. When the disease is detected early, it can be treated using medications like rifampicin, isoniazid and others. The bacteria causing tuberculosis can infect a person without causing any major symptoms, hiding inside the immune cells of our body, a phase called as the latent infection phase. When the symptoms show up (active infection), lungs are affected and if the disease has progressed further, it can affect other organs. The TB Confirmation Panel has three different components which help identify and confirm the tuberculosis infection.
What is the TB Confirmation Panel -GeneXpert, Smear & CultureTest Used For?
TB Confirmation Panel -GeneXpert, Smear & Culture test can be used to detect tuberculosis infection. It is recommended for people who have weaker immune systems, have been affected by this disease before, have been in constant contact with a person suffering from tuberculosis or are themselves showing symptoms of tuberculosis.
Symptoms of Tuberculosis
Some of the symptoms of an active infection of tuberculosis are
Cough lasting more than two – three weeks with or without blood
Fever and Night Sweats
Fatigue
Appetite loss
Unexplained weight loss
Pain in different parts of the body
Swollen glands
Which Tests are Included in TB Confirmation Panel -GeneXpert, Smear & Culture Test?
There are three components of this test, which are given below
GeneXpert Test
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This is a test which detects the presence of the genetic material of the bacteria in the sample, by amplifying it. This makes this test both specific and sensitive. This test also helps in finding whether the variant of bacteria present in the sample is resistant to the medications commonly used for tuberculosis, like rifampicin and isoniazid.
Acid Fast Bacillus Smear Test
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This test uses stains or dyes which stains the bacteria which causes tuberculosis, observed under the microscope. Other bacteria with similar properties as the tuberculosis bacteria may also be stained.
Culture test
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The bacteria causing tuberculosis is a slow growing bacteria. Depending on the medium used to grow the bacteria, which is also known as culture, this test can be time taking. But it is the most reliable test for checking the presence of the bacteria, which identify whether the bacteria present is resistant to any of the medications used.
Preparation for Test
Before the test, let your general physician know of any medication, supplements or treatments that you are taking or currently undergoing. The laboratory technician will help you collect the sputum sample or other samples of body fluids.
Interpretation of Test Results
Acid Fast Bacillus Smear Test: If this test is positive, it means that tuberculosis causing bacteria is present in the sample. This does not indicate the stage of tuberculosis infection. If this test is negative, it means that the bacteria is not present in the sample. Absence of this bacteria in the smear test does not guarantee that you are not infected.
GeneXpert Test: If this test is positive, it means that the genetic material of the tuberculosis causing bacteria is present in the sample. If this test is negative, it means that the genetic material of the bacteria is not present in the sample. As this test is much faster than the culture test, which can take more than a month, it helps the doctor decide patient treatment. But, this test should always accompany the culture test. This test does not indicate the stage of tuberculosis infection.
Culture Test: If the bacteria present in the sample grows in the medium within 42 days, the test is considered positive. If there are no bacteria in the sample, there would be no bacterial growth in the medium, and the test is considered negative.
FAQs
How is the sample collected for the TB Confirmation Panel -GeneXpert, Smear & Culture test?
A sputum sample can be collected for all the three tests. But other samples like blood sample, urine samples, other bodily fluids or tissues can also be used for these tests, depending on the patient’s age and the diagnostic laboratory.
What is the turnaround time (TAT) for TB Confirmation Panel -GeneXpert, Smear & Culture test?
The final tests results can take up to 43 days after the sample is taken. As the bacteria causing tuberculosis is a slow growing bacteria, the culture results take more time. The smear test and the GeneXpert test take lesser time, and may be reported earlier. TAT would also depend on the diagnostic laboratory that has taken the sample for analysis.
What should we do if the result of more than one components of this test come positive?
Please let your doctor interpret the results. It means that tuberculosis causing bacteria is present in your body. This may or may not indicate an active infection. Doctors may advise other tests to confirm the diagnosis. When detected early, tuberculosis can be treated effectively using first line medicines like rifampicin and others. Please ensure to take these medications and do not discontinue without consulting the doctor.
Can tuberculosis affects organs other than lungs?
Tuberculosis not only affects the lungs but other organs like brain, liver, spleen, intestines, etc. depending on the extent of the infection. Other parts of the body may also be affected.
Why is it important to do these three tests?
The smear test, stains only the bacteria causing tuberculosis. If the smear tests come negative, there is still a chance that you may have the infection, and the bacteria did not show up in the test.
The GeneXpert test, detects if the genetic material of the bacteria is present in the sputum sample. If there are symptoms of tuberculosis, this test would also help the doctor decide treatment options for the patient as it also indicates if the bacteria present in the sample is resistant to any of the medications usually prescribed for tuberculosis.
Though the GeneXpert test is highly specific and sensitive, the culture test is the most reliable, which by growing the bacteria confirms its presence. The extent of infection is then confirmed by other tests advised by the doctor.
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