From the Guidelines
Definition of Latent Tuberculosis
Latent tuberculosis (LTBI) is a condition in which an individual is infected with Mycobacterium tuberculosis, but does not exhibit symptoms or signs of active tuberculosis disease 1. Individuals with LTBI are at risk of progressing to active tuberculosis, with a lifetime risk estimated to be around 5-15% 1.
Key Characteristics
- One third of the world’s population is estimated to be infected with Mycobacterium tuberculosis 1.
- The vast majority of infected persons have no signs or symptoms of TB disease and are not infectious, but they are at risk for developing active TB disease and becoming infectious 1.
- The likelihood of progression of LTBI to active TB depends on bacterial, host, and environmental factors 1.
Treatment
Treatment of LTBI is effective in preventing progression to TB disease, with currently available regimens having an efficacy ranging from 60% to 90% 1. The standard treatment regimen for LTBI includes:
- Isoniazid (INH) 300mg daily for 9 months 1
- Alternatively, rifampin (RIF) 600mg daily for 4 months 1 The goal of treatment is to achieve a cure rate of at least 90% and prevent the progression to active TB disease 1.
Considerations
The potential benefit of treatment needs to be carefully balanced against the risk of drug-related adverse events 1. For infected individuals in population groups with a high risk of progression to active disease, the anticipated benefits are usually greater than the potential harms 1.
From the Research
Definition of Latent Tuberculosis (TB)
- Latent tuberculosis infection (LTBI) refers to a condition where viable Mycobacterium tuberculosis (MTB) bacilli are present in an individual, but symptoms and signs of active disease are lacking, and the bacilli are relatively inactive metabolically 2.
- LTBI is a condition in which a person is infected with Mycobacterium tuberculosis, but does not currently have active tuberculosis disease 3.
- It is characterized by a positive tuberculin skin test in the absence of clinical or radiological signs of active tuberculosis disease 4.
- LTBI is defined as a state of persistent immune response to stimulation by Mycobacterium tuberculosis antigens without evidence of clinically manifested active tuberculosis (TB) 5.
Diagnosis and Treatment of Latent Tuberculosis (TB)
- Diagnosis of LTBI is typically done using tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) 3, 5.
- Treatment of LTBI is designed to prevent the progression from asymptomatic infection to symptomatic, potentially lethal, active disease 2.
- The treatment of choice for LTBI is isoniazid for nine months, with hepatotoxicity being the most severe adverse effect 3.
- Other treatment regimens include once-weekly isoniazid plus rifapentine for 3 months, daily rifampin for 4 months, and daily isoniazid plus rifampin for 3-4 months 6.
- Novel vaccine strategies, host immunity-directed therapies, and ultrashort antimicrobial regimens for TB prevention are under evaluation 6.