Patients were divided into four categories for analysis: those with smear- and culture-positive pulmonary tuberculosis; those with smear-negative, culture-positive pulmonary tuberculosis; those with no bacteriologic evidence of tuberculosis who had improvement without treatment (no tuberculosis); and those who were smear- and culture-negative for pulmonary tuberculosis who nonetheless were treated for tuberculosis on the basis of clinical and radiologic findings (clinical tuberculosis). A smear-positive case was defined as at least two smears of scanty grade (1 to 10 acid-fast bacilli per 100 fields) or one or more smears of 1+ or more (10 to 99 bacilli per 100 fields). A culture-positive case was defined as positive results on at least one of four culture vials. Because a clear final diagnosis was required, patients with an indeterminate diagnosis were excluded from the main analysis if there was a negative culture result while the patient was receiving tuberculosis treatment (for patients with suspected multidrug resistance), contamination of at least three of four cultures, growth of nontuberculous mycobacteria only, indeterminate phenotypic rifampin susceptibility, a negative culture with a positive sputum smear, or suspected cross-contamination of cultures (i.e., only one of four cultures had positive results after >28 days to growth in MGIT or <20 colonies in Löwenstein–Jensen medium) or if the patient died or was lost to follow-up.