42 - Positive Screening Test for Tuberculosis

Abstract

Nearly one-fourth of the world’s population (1.7 billion people) have latent tuberculosis (TB) infection, of whom 5–10% will develop active TB without preventive therapy. Identification and treatment of individuals with latent TB infection are necessary to control and eventually eliminate TB; however, current tests—tuberculin skin tests and interferon-gamma release assays—are unable to distinguish latent infection from active disease. Tuberculin skin tests and interferon-gamma release assays measure the cellular immune response to Mycobacterium tuberculosis, thus providing immunologic evidence of prior exposure. These tests are most appropriately used to screen asymptomatic high-risk individuals for latent TB infection. This chapter describes the goals of M. tuberculosis infection testing, indications for testing, tuberculin skin tests and interferon-gamma release assays plus test interpretation, approach to individuals with suspected M. tuberculosis infection, and treatment regimens for latent TB infection.