Latent Tuberculosis

The treatment of latent tuberculosis infection (LTBI) is essential to controlling and eliminating TB by reducing the risk that TB infection will progress to disease.

The terms "preventive therapy" and "chemoprophylaxis" have been used for decades and are preferred in the UK because it involves giving medication to people who have no active disease and are currently well, the reason for treatment is primarily to prevent people from becoming unwell. The term "latent tuberculosis treatment" is preferred in the US because the medication does not actually prevent infection: it prevents an existing silent infection from becoming active. The feeling in the US is that the term "treatment of LTBI" promotes wider implementation by convincing people that they are receiving treatment for disease. There are no convincing reasons to prefer one term over the other.

It is essential that assessment to rule out active TB is carried out before treatment for LTBI is started. To give LTBI treatment to someone with active TB is a serious error: the TB will not be adequately treated and there is a risk of developing drug-resistant strains of TB.

There are several treatment regimens available:

• 9H—Isoniazid for 9 months is the gold standard and is 93% effective.
• 6H—Isoniazid for 6 months might be adopted by a local TB program based on cost-effectiveness and patient compliance. This is the regimen currently recommended in the UK for routine use. The US guidance exclude this regimen from use in children or persons with radiographic evidence of prior tuberculosis (old fibrotic lesions). (69% effective)
• 6 to 9H₂—A twice-weekly regimen for the above 2 treatment regimens is an alternative if administered under Directly observed therapy (DOT).
• 4R—Rifampicin for 4-months is an alternative for those who are unable to take isoniazid or who have had known exposure to isoniazid-resistant TB.
• 3HR—Isoniazid and rifampicin may be given for three months.

2RZ—The two month regimen of rifampicin and pyrazinamide is no longer recommended for treatment of LTBI because of the greatly increased risk of drug-induced hepatitis and death.