One hundred thirty patients including 30 elderly patients with active TB that had been confirmed by positive results of cultures of sputum, BAL fluid, pleural fluid, peritoneal fluid, or lymph node tissue samples were prospectively enrolled between April 2005 and June 2007. This study was approved by the ethics committee of each institution. The patients with active TB received their diagnoses at Kawasaki Medical School Hospital (1,072 beds), Kawasaki Medical School Kawasaki Hospital (650 beds), Kurashiki Central Hospital (1,570 beds), Kurashiki Daiichi Hospital (192 beds), or Asahigaoka Hospital (90 beds). We obtained written, informed consent from all patients in this study. All patients had either negative responses to serological tests for HIV or had no obvious risk factors for HIV infection. Subjects were divided into the following two groups: group 1 consisted of 30 elderly patients (≥ 80 years old) with active TB; and group 2 consisted of the remaining 100 younger patients (< 80 years old) with active TB. From patients in both groups with active TB, we collected demographic data regarding (1) any history of previous TB infection or antituberculous treatment, (2) other underlying diseases (ie, respiratory diseases such as healed pulmonary TB or COPD, and nonrespiratory diseases such as malignant disease, including leukemia, diabetes mellitus, renal failure with hemodialysis, collagen vascular disease, neurologic disease, GI disease, cardiovascular disease, and HIV infection), and (3) the receipt of immunosuppressive drugs within 3 months before enrollment into this study. Information regarding any previous Mantoux TST results and BCG vaccination inoculation, as well as information about laboratory findings (ie, WBC count, lymphocyte count, total protein concentration, and albumin concentration) and radiologic findings (ie, portion, extension, and cavity) were collected at the time of enrollment. Sputum or other appropriate respiratory samples were collected from all patients, and culture samples were obtained for the detection of mycobacteria.