Tuberculosis (TB) is a bacterial infection caused by Mycobacterium tuberculosis. The disease primarily affects the lungs but can also affect other parts of the body, such as the brain, kidneys, and spine.
According to the World Health Organization (WHO), TB is one of the top 10 causes of death worldwide and the leading cause of death from a single infectious agent, ranking above HIV/AIDS. Although TB is a curable disease, it remains a major public health challenge, especially in low- and middle-income countries.
Traditional Tuberculosis Diagnosis
Traditionally, TB diagnosis has been based on a combination of clinical evaluation and laboratory tests.
Sputum smear microscopy, which involves examining sputum under a microscope to detect the presence of TB bacteria, has been the primary diagnostic tool for decades. However, this method has several limitations:.
- It can be difficult to obtain sputum samples, especially in children and those with HIV/AIDS.
- The technique is not very sensitive, meaning that a negative result does not rule out TB infection.
- It is unable to distinguish between active and latent TB infections.
Modernization of Tuberculosis Diagnosis
Recently, several new diagnostic tools have been developed to improve TB diagnosis. These tools are faster, more accurate, and more convenient than traditional methods. The following are some of the modern diagnostic tools currently available:.
GeneXpert MTB/RIF
The GeneXpert MTB/RIF is a cartridge-based nucleic acid amplification test that simultaneously detects the presence of TB bacteria and resistance to the antibiotic rifampicin.
The machine can produce results within two hours and is highly sensitive and specific. GeneXpert MTB/RIF is currently the most widely used modern diagnostic tool for TB, especially in low- and middle-income countries.
Line Probe Assays
Line probe assays are molecular tests that detect specific genetic sequences of TB bacteria. These tests can detect drug resistance and provide results within two days.
The Xpert MTB/RIF Ultra is a newer version of the GeneXpert MTB/RIF that incorporates a line probe assay for improved sensitivity.
LAM Tests
Lipoarabinomannan (LAM) tests detect a component of TB bacteria in urine samples of HIV-positive patients with advanced TB. These tests have high specificity but low sensitivity.
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LAM tests are useful in diagnosing disseminated TB in HIV-positive patients who are unable to produce sputum samples.
Chest X-Rays
Chest X-rays are useful in detecting TB infection in patients with pulmonary symptoms. However, chest X-rays cannot distinguish between active and latent TB infections.
The use of digital chest X-rays and computer-aided diagnosis software can improve accuracy and speed up diagnosis.
Bacteriophage-Based Tests
Bacteriophages are viruses that infect and kill bacteria. Bacteriophage-based tests use engineered bacteriophages to detect the presence of TB bacteria in sputum samples.
These tests are faster than traditional sputum smear microscopy and have comparable sensitivity and specificity.
Blood Tests
Blood tests detect immune responses to TB bacteria in the blood. Two types of blood tests are currently available:.
- The interferon-gamma release assay (IGRA) measures the release of interferon-gamma in response to TB antigens.
- The TB serological test measures the levels of antibodies to TB bacteria in the blood.
Although blood tests are convenient and do not require sputum samples, they have limited sensitivity and are unable to distinguish between active and latent TB infections.
Conclusion
The modernization of TB diagnosis has greatly improved the accuracy and speed of TB diagnosis.
Although some of the modern diagnostic tools are expensive and may not be widely available in low- and middle-income countries, they have the potential to reduce the burden of TB worldwide. Further research is needed to develop even more accurate and affordable diagnostic tools for TB.
