What is the difference between latent tuberculosis (TB) and active tuberculosis (TB)?

From the Guidelines

Latent TB should be treated to prevent progression to active TB, with the most effective regimen being 9 months of isoniazid, as recommended by the World Health Organization for high-risk individuals in low TB burden countries 1. When considering the management of latent tuberculosis infection (LTBI), it is crucial to distinguish it from active TB, as the treatment approaches and outcomes differ significantly. Latent TB is characterized by the presence of immune responses to previously acquired Mycobacterium tuberculosis infection without clinical evidence of active tuberculosis. The World Health Organization guidelines for low TB burden countries strongly recommend systematic testing and treatment of LTBI in high-risk individuals, including those living with HIV, contacts of pulmonary TB cases, and patients with certain medical conditions 1. Key points to consider in the management of LTBI include:

• The use of either commercial interferon-gamma release assays or Mantoux tuberculin skin testing to diagnose LTBI 1
• Chest radiography should be performed before LTBI treatment to rule out active TB disease 1
• Recommended treatment regimens for LTBI include 6 or 9 months of isoniazid, 12 weeks of rifapentine plus isoniazid, 3-4 months of isoniazid plus rifampicin, or 3-4 months of rifampicin alone 1 In contrast, active TB requires a more intensive treatment regimen, typically including four drugs (isoniazid, rifampin, ethambutol, and pyrazinamide) for 2 months, followed by isoniazid and rifampin for an additional 4 months. It is essential to note that the treatment of LTBI is critical in preventing the progression to active TB, especially in high-risk individuals. According to the American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America guidelines, 9 months of isoniazid is recommended for individuals with abnormal chest radiographs consistent with prior tuberculosis 1. Overall, the management of LTBI should prioritize the prevention of active TB, and treatment regimens should be tailored to the individual's risk factors and medical history. The most effective treatment regimen for LTBI is 9 months of isoniazid, as it has been shown to significantly reduce the risk of progression to active TB 1.

From the FDA Drug Label

Isoniazid is recommended for all forms of tuberculosis in which organisms are susceptible. However, active tuberculosis must be treated with multiple concomitant antituberculosis medications to prevent the emergence of drug resistance. Isoniazid is recommended as preventive therapy for the following groups, regardless of age.

The main difference between latent and active TB is that latent TB is a condition where the person is infected with TB bacteria, but the bacteria are not active and the person is not sick, while active TB is a condition where the bacteria are active and the person is sick.

• Latent TB is treated with isoniazid as preventive therapy to prevent the development of active TB.
• Active TB must be treated with multiple concomitant antituberculosis medications to prevent the emergence of drug resistance. 2

From the Research

Latent vs Active TB

• Latent tuberculosis infection (LTBI) is a condition where a person is infected with Mycobacterium tuberculosis, but does not show any symptoms of active TB disease 3, 4, 5, 6, 7.
• Active tuberculosis (TB) is a condition where a person has symptoms of TB disease, such as coughing, fever, and weight loss, and can transmit the disease to others 4, 5.

Treatment of Latent TB

• The treatment of LTBI is an important component of TB control and elimination, and can reduce the risk of developing active TB disease 3, 4, 5, 6, 7.
• Treatment regimens for LTBI include:
  • Once-weekly isoniazid plus rifapentine for 3 months 3, 5, 7
  • Daily rifampin for 4 months 3, 7
  • Daily isoniazid plus rifampin for 3-4 months 3
  • Daily isoniazid for 6-9 months 3, 6, 7
• These regimens have been shown to be effective in preventing the progression of LTBI to active TB disease, with completion rates varying depending on the regimen and patient population 3, 5, 6, 7.

Treatment of Active TB

• The treatment of active TB typically involves a combination of four essential tuberculosis drugs: isoniazid, rifampicin, pyrazinamid, and ethambutol, with streptomycin sometimes used as an alternative to ethambutol 4, 5.
• The treatment regimen for active TB typically consists of an initial intensive phase followed by a consolidation phase, with drugs administered in the morning on an empty stomach one hour before meals 4.
• Directly-observed therapy (DOT) is the standard of care for pulmonary TB, with virtual treatment monitoring using digital technologies becoming more common as a way to provide a more patient-centered approach to care 5.