Latent tuberculosis infection (LTBI) is defined as a condition in which an individual has a positive tuberculin skin test (TST) caused by Mycobacterium tuberculosis infection, excluding responses due to Bacillus Calmette–Guérin (BCG) vaccination, and exhibits no radiographic or clinical evidence of active tuberculosis.
Key Diagnostic Points
Medical History
A history of contact with tuberculosis patients is commonly observed.
Clinical Manifestations
Patients may or may not exhibit symptoms of tuberculosis-related toxicity, and physical examination may reveal no positive findings.
Chest X-Ray Examination
Normal findings are typically observed.
Tuberculin Skin Test (TST)
The test result is positive.
Differential Diagnosis
Chronic tonsillitis, recurrent upper respiratory tract infections, urinary tract infections, and rheumatic fever should be considered for differentiation.
Treatment
The goal of preventive treatment is to eliminate M. tuberculosis in the body, thereby preventing progression to active tuberculosis in the future. This serves as a critical measure in the prevention and control of tuberculosis. Preventive anti-tuberculosis treatment is recommended for the following situations:
- Individuals vaccinated with BCG but showing an increase in induration diameter of ≥10 mm in the TST within the past 2 years, which may indicate a natural infection.
- Recent natural infections where the TST has converted from negative to positive.
- Infants and adolescents with strongly positive TST results.
- Individuals with positive TST results accompanied by early symptoms of tuberculosis-related toxicity.
- Patients with positive TST results who require corticosteroids or other immunosuppressive agents for other diseases.
- Children with positive TST results who have recently contracted measles or pertussis.
- Patients with positive TST results who are infected with human immunodeficiency virus (HIV) or diagnosed with acquired immunodeficiency syndrome (AIDS).
The following treatment regimens are commonly used:
- Isoniazid (INH): Administered as a single agent at a dose of 10 mg/kg daily for 6 or 9 months (6/9 INH), with a maximum daily dose of 300 mg.
- Isoniazid and Rifampin (INH+RFP): Combined therapy at doses of 10 mg/kg/day for INH and 15 mg/kg/day for RFP for 3–4 months (3/4 INH+RFP). The maximum daily dose of RFP is limited to 600 mg.
- Rifampin (RFP): Administered as a single agent at a dose of 15 mg/kg/day for 3–4 months (3/4 RFP) as an alternative regimen.