The diagnosis of pulmonary tuberculosis can be made by the detection of acid fast bacilli by direct microscopy, using carbol fuchsin stain and/or fluorochrome stain. Microscopy is a rapid method but lacks sufficient sensitivity and does not distinguish between different species of mycobacteria. The sensitivity of microscopy is often not more than 25-40% as compared to culture, but under ideal conditions, it is possible to achieve a rate of 60-70%. The average rate obtained in India is 12-15%, but microscopy is still the mainstay of the tuberculosis control programme of the developing countries, including India. The fluorochrome stain technique is.
