Last Updated on February 16, 2023 by Shabnam Sengupta
Tuberculosis (TB) is a major global public health problem that causes substantial morbidity and mortality in humans. Until the COVID-19 pandemic, tuberculosis was the leading cause of death from a single infectious agent, outranking a number of other diseases. Tuberculosis is caused by Mycobacterium tuberculosis, one of the world’s most virulent pathogens. It has coexisted with humans for a thousand years and remains a major public health threat, killing more than 1 million people each year. Tuberculosis control necessitates early detection and effective treatment. This article focuses on individuals who are at a higher risk of developing tuberculosis and the ways in which it is diagnosed.
Who should be tested for tuberculosis?
The majority of suspected tuberculosis cases necessitate TB testing. These primarily include prolonged and close contact with a person who has been diagnosed with tuberculosis. Infection is influenced by the duration of exposure, the age of the individual, the time of contact, and the contact’s immunological status.
What conventional types of tests are used to detect tuberculosis?
Tuberculosis is typically detected through screening and confirmatory testing. There are two types of TB screening tests: the tuberculin skin test (TST) and the interferon gamma release assay (IGRA).
A healthcare provider will inject a small amount of purified protein derivative (PPD) under the skin of your forearm for the TST. After two to three days, you must return to the healthcare provider for an examination of the injection site. A healthcare provider will draw blood for the IGRA and send the sample to the lab.
Only a microbiological examination of samples can provide a definitive diagnosis of tuberculosis. Unfortunately, even these methods are not completely sensitive. Despite the presence of active TB, all microbiological methods will produce negative results in 10% to 15% of cases. All microbiological methods are highly specific, but their sensitivity is heavily dependent on the quality of the obtained specimen and how it is handled. The first is direct smear microscopy using the Ziehl-Nielsen technique, which is still the primary tool for tuberculosis diagnosis and monitoring, and the second is mycobacteria culture. Culture, when combined with species identification, is the only technique that reliably confirms the presence of tuberculosis.
What are the other tuberculosis identification tests?
Additional tests to determine whether an infection is active or whether your lungs are infected include:
- Advances in Lung Fluid Testing
- X-ray of the chest: Although neither extrapulmonary nor pulmonary TB has a pathognomonic radiographic sign, diagnostic suspicion in pulmonary disease is primarily based on indicative radiographic findings.
- CT scans (computed tomography): High-resolution computed tomography (CT) is now used to distinguish between active lesions and evidence of prior disease.
- Non-sputum based tests are still in the developmental stage. These primarily include urinary lipoarabinomannan for patients with TB-HIV coinfection, paediatric stool processing prior to Xpert, blood host marker, skin patches, and breath tests.
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