Microscopy positive and microscopy negative cases of pulmonary tuberculosis.

Abstract

The national tuberculosis programs of the developing countries are based on finding and treating cases in which microscopy of the sputum reveals tubercle bacilli. Neither the effect of exclusion of cases in which microscopy reveals no tubercle bacilli (microscopy negative) but in which cultures of the sputum do demonstrate the organisms, nor the value of microscopy or culture in the diagnosis of pulmonary tuberculosis, seem to have been studied adequately. Data from three successive prevalence surveys in a sizeable random sample of villages showed that patients whose sputum revealed tubercle bacilli by microscopy constituted 39 per cent of the total subjects in whom sputum cultures yielded the organisms, and they had more extensive disease as revealed radiographically, and were more infectious to household contacts than were the patients whose sputum was shown to contain tubercle bacilli only by culture. Because of the meager facilities for treatment available in developing countries and the high defaulte...