Contacts of infectious tuberculosis patients: monitor those at highest risk of developing tuberculosis.

It is essential to identify and treat contacts of tuberculosis patients with active disease. Persons exposed through close, prolonged or frequent contact may develop tuberculosis, usually within two years following exposure. What is the harm-benefit balance of tuberculosis prophylaxis in contacts at risk? To answer this question, we conducted a review of the literature, using the standard Prescrire methodology. Standard prophylaxis for pulmonary tuberculosis consists of isoniazid monotherapy for 6 to 12 months.This regimen has been tested in randomised placebo-controlled trials involving tens of thousands of persons with a positive tuberculin skin test (TST). Pulmonary tuberculosis occurred in 0.6% of patients in the isoniazid groups versus 1.7% in the placebo groups, after a follow-up of at least 2 years. However, isoniazid can cause severe hepatic disorders and numerous drug interactions. Rifampicin monotherapy was shown to be effective in only one placebo-controlled trial in patients with silicosis, who have a very high risk of developing tuberculosis. Rifampicin also carries a high risk of drug interactions but is less hepatotoxic than isoniazid. A 3-month course of the isoniazid+ rifampicin combination had a similar harm-benefit balance as a 6- or 9-month course of isoniazid monotherapy. The rifampicin + pyrazinamide combination is no more effective than isoniazid monotherapy but has more hepatic adverse effects. British guidelines issued in 2011 recommend treatment for contacts who have signs of latent tuberculosis infection, based mainly on a positive TST or gamma interferon release assay, and are at high risk of developing active tuberculosis. patients aged at least 2 years who are strongly suspected of having latent tuberculosis infection: either tuberculosis treatment, or chest radiography 3 and 12 months after initial diagnosis. In practice, contacts of infectious patients have a low risk of developing clinical tuberculosis.Treatment reduces the risk of tuberculosis but exposes a large number of persons to numerous, sometimes serious, adverse effects. Watchful waiting for 2 years, without treatment, is often the best option.