From the Guidelines
The chances of developing active TB after 15 years of latent tuberculosis infection (LTBI) with a small lung granuloma and no history of active disease are quite low, approximately 5-10% lifetime risk, with most of this risk concentrated in the first 2-5 years after infection, as stated in the 2015 WHO guidelines for low tuberculosis burden countries 1. After 15 years without progression, your risk is even lower, likely less than 1-2%. This reduced risk occurs because the immune system has effectively contained the TB bacteria within the granuloma, preventing their spread and multiplication. However, certain factors could increase this risk, including:
- HIV infection
- Diabetes
- Immunosuppressive medications
- Malnutrition
- Other conditions that weaken the immune system Despite the low risk, you might consider preventive treatment if not previously treated, typically consisting of:
- Isoniazid (300mg daily for adults) for 6-9 months
- Rifampin (600mg daily) for 4 months
- The combination of isoniazid and rifapentine once weekly for 12 weeks, as recommended in the 2020 guidelines for the treatment of latent tuberculosis infection by the National Tuberculosis Controllers Association and CDC 1 These treatments can reduce the risk of progression by 60-90%. Regular monitoring with a healthcare provider is recommended, especially if you develop symptoms such as:
- Persistent cough
- Weight loss
- Night sweats
- Fever, which could indicate TB reactivation.
From the FDA Drug Label
Persons with abnormal chest radiographs that show fibrotic lesions likely to represent old healed tuberculosis (≥ 5 mm) The FDA drug label does not answer the question.
From the Research
Chances of Developing Active TB
The chances of developing active TB after 15 years of latent TB infection (LTBI) with a small lung granuloma and no active disease ever are not directly stated in the provided studies. However, the studies do provide information on the treatment and prevention of LTBI.
Treatment of LTBI
- A 9-month regimen of isoniazid can prevent active tuberculosis in persons with LTBI 2.
- A 4-month regimen of rifampin is not inferior to the 9-month regimen of isoniazid for the prevention of active tuberculosis and is associated with a higher rate of treatment completion and better safety 2, 3.
- Treatment of LTBI with 4 months of rifampin leads to fewer serious adverse events and better adherence than 9 months of isoniazid 3.
- A 3-month regimen of rifapentine and isoniazid is as effective as 9 months of isoniazid alone in preventing tuberculosis and has a higher treatment-completion rate 4.
Efficacy of Treatment Regimens
- The use of rifapentine plus isoniazid for 3 months was as effective as 9 months of isoniazid alone in preventing tuberculosis 4.
- A 6-week monotherapy regimen of rifapentine (6wP) is predicted to result in equal or better efficacy than 1HP and 3HP for LTBI treatment without the potential added toxicity of isoniazid 5.