An infectious case of pulmonary tuberculosis is diagnosed by demonstrating tubercle bacilli in sputum. The laboratory methods available for this purpose are sputum microscopy, isolation of tubercle bacilli in culture followed by identification of the bacilli and animal pathogenicity tests. Evidence based on all the three methods establishes bacteriological diagnosis beyond any doubt, but even economically advanced countries may not consider such an elaborate procedure essential for routine diagnosis. Very often sputum microscopy alone is considered sufficient for diagnosis, when combined with clinical findings. Therefore a realistic and economical approach for developing countries would be to provide only facilities for sputum microscopy
