Pulmonary Tuberculosis: Diagnosis, Treatment and Long-Term Consequences

Tuberculosis (TB) is a communicable disease caused by the bacterium Mycobacterium tuberculosis. While it can affect various organs (extrapulmonary TB), it most frequently involves the lungs, presenting as Pulmonary Tuberculosis.

TB remains a significant global public health issue. However, with appropriate diagnostic evaluation and adherence to established medical therapy, drug-susceptible TB is generally a curable condition.

Transmission and Pathogenesis

Mycobacterium tuberculosis is transmitted via the airborne route. When an individual with active pulmonary TB coughs or speaks, they may expel droplet nuclei containing the bacilli. Inhalation of these droplets by another person can lead to infection.

Many individuals who become infected do not develop active disease. Their immune system may contain the infection, resulting in Latent TB Infection (LTBI), which is asymptomatic and non-communicable. If immune containment fails—either initially or years later—the infection can progress to Active TB Disease.

Symptoms and Clinical Presentation

The onset of active pulmonary TB can be gradual, and symptoms may develop over weeks or months.

Common clinical features include:

• A persistent cough, often lasting several weeks.
• Expectoration of sputum, which may be purulent or blood-streaked, or episodes of frank hemoptysis.
• Fever, which may be low-grade.
• Night sweats.
• Unintentional weight loss and anorexia.
• Fatigue.
• Breathlessness or chest pain, depending on the extent of lung parenchyma or pleural involvement.

Diagnostic Evaluation

Establishing a diagnosis of TB typically involves microbiological confirmation, alongside clinical and radiological assessment.

Microbiological and Molecular Investigations

Current World Health Organization (WHO) guidelines emphasize the importance of rapid and accurate diagnosis ^[1].

• Rapid Molecular Diagnostics: WHO strongly recommends the use of WHO-recommended rapid diagnostics (mWRDs), such as Xpert MTB/RIF or Truenat, as the initial diagnostic test for suspected pulmonary TB. These tests detect the DNA of the TB bacilli and can simultaneously identify resistance to key medications like rifampicin.
• Sputum Culture: Culture methods remain important for phenotypic drug-susceptibility testing (DST) and monitoring in specific clinical scenarios, though they require longer turnaround times.
• Smear Microscopy: While historically the primary initial test, it is less sensitive than molecular methods. It may still be utilized for monitoring treatment response or in settings where molecular testing is not yet accessible.

Imaging

• Chest Radiograph (X-ray): Frequently used to assess for features suggestive of TB, such as upper lobe infiltrates or cavitation. However, radiographic findings alone are generally not sufficient for a definitive microbiological diagnosis.

Treatment Principles

The treatment of active, drug-susceptible pulmonary TB requires a combination of antimicrobial agents to effectively eradicate the bacteria and prevent the emergence of drug resistance. Monotherapy is not appropriate for active TB.

Treatment regimens are guided by international and national protocols ^{[2] [3]}. The selection of a specific regimen depends on clinical factors, the drug susceptibility profile of the bacteria, and local programmatic guidelines.

• Standard Regimens: Traditionally, a widely used regimen consists of a 6-month course involving an intensive phase with multiple drugs (e.g., isoniazid, rifampicin, pyrazinamide, and ethambutol) followed by a continuation phase with fewer drugs.
• Shorter Regimens: Current guidelines also recognize the efficacy of certain 4-month regimens for specific populations with drug-susceptible pulmonary TB, reflecting ongoing advancements in TB therapeutics.

The Importance of Adherence

Completing the full course of prescribed therapy is critical. Interruption of treatment can lead to treatment failure and promotes the development of drug-resistant TB, which requires more complex and prolonged therapeutic strategies.

Long-Term Considerations

While microbiological cure is the primary goal of treatment, pulmonary TB can result in residual structural changes in the lungs. A proportion of patients may experience persistent respiratory symptoms or physiological impairment even after successful treatment, a spectrum of conditions recognized as Post-Tuberculosis Lung Disease (PTLD).

When to Seek Medical Attention

Individuals experiencing symptoms compatible with TB, such as a prolonged cough, fever, and weight loss, should seek medical evaluation. Urgent assessment is indicated for acute complications, such as significant hemoptysis or sudden, severe breathlessness.