Introduction
Tuberculosis (TB), which is caused by bacteria of the Mycobacterium
tuberculosis complex, is one of the oldest diseases known to affect
humans and a leading cause of death worldwide (1).
Approximately one-third of the global population is infected with a
lifetime risk of 10% for developing tuberculosis (TB) disease. In 2017,
there were 10.4 million reported cases of TB worldwide, corresponding to
an incidence rate of 133 cases per 100,000 individuals. Among these
cases, 90% were adults over the age of 15, and 64% were male. (2).
Iran is considered a high-burden country for tuberculosis, with a
notable incidence rate. The endemicity of TB in this region increases
the pretest probability of the disease in patients presenting with
compatible symptoms and radiological findings (3). Pulmonary TB is
usually a disease having a gradual onset. Fever is the most common
observed constitutional symptom which characteristically develops in the
late afternoon. There may be other manifestations in up to 75% of cases
of pulmonary TB, such as malaise, weakness, unusual fatigue, headache,
night sweats and weight loss. This is usually accompanied by caseous
necrosis and concomitant caseous liquefaction and cough and purulent
sputum which is often associated with mild hemoptysis (4).
Sputum smear microscopy and culture are commonly used for the diagnosis
of pulmonary TB. However, it’s essential to recognize the limitations of
these tests (5, 6). Smear microscopy has a sensitivity ranging from
36.9% to 55.6% and specificity of around 99%, while culture has
higher sensitivity (approximately 80-90%) but takes longer for results
(7, 8). Importantly, negative smear and culture results do not exclude
the diagnosis of TB, especially in cases of paucibacillary disease or
extrapulmonary involvement (8).