Diagnosis of sputum smear- and sputum culture-negative pulmonary tuberculosis

A group of patients with new or enlarging apical lung lesions thought to be tuberculous was randomly selected for observation without treatment. All were tuberculin-positive and all had sputum negative for Mycobacterium tuberculosis on direct examination and on culture. Of the 152 patients, 88 (58%) developed bacteriologically confirmed pulmonary tuberculosis during a follow-up period of up to 65 months.