[Latent tuberculosis infection: diagnosis and treatment]

The essential component of tuberculosis elimination strategy is to identify and treat persons with latent tuberculosis infection (LTBI) who are at high risk for developing active tuberculosis. The tuberculin skin test is the only proven method for identifying LTBI. Although the specificity and the sensitivity are decreased by cross reaction with BCG vaccination and by non tuberculous mycobacteria, there is no better diagnostic tool. The test's positive predictive value is poor in populations with low risk for tuberculosis. Identification of persons with LTBI is focused on groups at high risk who would benefit from therapy (targeted tuberculin testing). The interpretation of the tuberculin skin test reaction is dependent on the risk factors and the immune status of the patient. For the past 30 years, Isoniazid has been the drug of choice for treating patients with LTBI, but its application has been limited by poor compliance and toxicity. Therefore, there has been interest in the development of shorter course treatments such as rifampin (4 months) or rifampin and pyrazinamide (2 months). We describe the new guidelines for targeted tuberculin testing and different treatment regimens for LTBI as recommend by the American Thoracic Society.