Sputum examination in the screening and diagnosis of pulmonary tuberculosis in the elderly.

Pulmonary tuberculosis is not uncommon in the elderly, particularly those in institutions, and is notoriously difficult to diagnose. Few bacilli are excreted by individuals with non-cavitating disease and positive cultures are usually required to confirm the diagnosis. Radiography is a poor screening method, and the role of the Mantoux test in this population controversial. The value of sputum culture as a screening procedure in elderly people with a productive cough was therefore investigated. In a prospective surveillance study over 26 months, all permanent residents in homes for the elderly were entered on the basis of a productive cough for 3 weeks or more irrespective of any known or presumed cause. Both smears and cultures were performed on sputum specimens, and Mantoux tests and chest radiographs were performed on those who were sputum positive. The 205 subjects investigated yielded 446 smears, seven of which were positive for acid-fast bacilli, and 433 cultures, 32 of which were positive for M. tuberculosis. From this 19 patients with pulmonary tuberculosis were identified, 18 of whom had non-cavitating disease on chest radiography. The numbers of bacilli in these patients were shown to be low and the excretion pattern haphazard. Smears were not sufficiently sensitive to diagnose non-cavitating tuberculosis in this population, and the sputum must be cultured in order to exclude the diagnosis. Four negative cultures are required in order to exclude the presence of pulmonary tuberculosis.