Volume 134, Issue 2, Pages 471-472 (August 2008) Clinical Utility of the Interferon-γ Release Assay for Elderly Patients With Active Tuberculosis  Jean-Paul Janssens, MD  CHEST  Volume 134, Issue 2, Pages 471-472 (August 2008) DOI: 10.1378/chest.08-0434 Copyright © 2008 The American College of Chest Physicians Terms and Conditions

Figure 1 Relationship between pretest and posttest probability of disease with a test having a sensitivity of 77% and a specificity of 97% (ie, that of QFT-2G [Bayes theorem]).6 The upper curve yields posttest probability if the test result is positive and the lower curve if the test result is negative. Pretest probability depends on estimated prevalence of disease in the population studied. Doted arrows show a pretest probability of 80% (estimated prevalence of LTBI in subjects aged >80 years), and a posttest probability of LTBI or TB of 50% if the QFT-2G result is negative. CHEST 2008 134, 471-472DOI: (10.1378/chest.08-0434) Copyright © 2008 The American College of Chest Physicians Terms and Conditions