In Reply: Thank you for your interesting and appropriate comments. The workup and testing of patients with suspected tuberculosis is clearly different in countries with a higher prevalence of tuberculosis than in countries with a lower prevalence. I appreciate that both the purified protein derivative and the interferon-gamma-release assay have very limited utility in the evaluation for active tuberculosis when there is a very high background prevalence of latent tuberculosis infection. In low-prevalence countries like the United States, tuberculosis is often considered in the differential diagnosis even when other infections or lung cancer is more likely. The tests for latent tuberculosis are considered quite important in the workup of active tuberculosis in this setting.