Tuberculosis
TB requires a stepped diagnostic pathway: smear, rapid molecular testing, culture, and drug susceptibility testing each answer a different question.
Tuberculosis, caused by Mycobacterium tuberculosis complex, remains a major cause of illness and death. Pulmonary TB is the commonest form; extrapulmonary disease requires specimen-specific testing.
Modern TB diagnosis is algorithmic: smear microscopy for rapid screening, rapid molecular tests (e.g., Xpert MTB/RIF) for detection and rifampicin resistance, line probe assays for first- and second-line resistance, and culture (MGIT/solid media) with phenotypic DST to confirm viability and guide treatment of drug-resistant disease. Whole genome sequencing adds detailed resistance and strain characterisation in selected cases. No single test replaces the others.