How is it Diagnosed?
Tuberculosis (TB), caused by Mycobacterium tuberculosis, primarily affects the lungs
but can also involve extrapulmonary sites. Diagnosis begins with clinical suspicion
based on symptoms such as chronic cough, hemoptysis, fever, night sweats, weight
loss, and fatigue.
The Mantoux tuberculin skin test (TST) or interferon-gamma release assays (IGRA) such
as QuantiFERON-TB Gold are used to detect latent TB infection. For active TB, the
diagnostic process centers on detecting the bacterium.
Sputum analysis is fundamental. Sputum smear microscopy for acid-fast bacilli (AFB)
using Ziehl-Neelsen staining provides a rapid, though less sensitive, test. Sputum
culture, particularly on Lowenstein-Jensen medium, remains the gold standard despite
requiring several weeks for results.
Nucleic acid amplification tests (NAATs), including CBNAAT (Cartridge-Based Nucleic
Acid Amplification Test) or GeneXpert, offer rapid, sensitive detection and can identify
rifampicin resistance. These are especially valuable in high-burden areas.
Chest X-ray typically shows upper lobe infiltrates, cavitary lesions, or nodular opacities
in pulmonary TB. For extrapulmonary TB, imaging varies—CT, MRI, or ultrasound are
chosen based on the affected organ.
Other investigations include biopsy and histopathology of lymph nodes or tissue
lesions, pleural fluid analysis, and CSF examination in suspected TB meningitis. HIV
testing is often concurrently performed due to high co-infection rates.
Timely diagnosis ensures prompt initiation of anti-tubercular therapy (ATT) to control
disease progression and reduce transmission.