Hello, Sputum smear and Culture will show positive results only in active TUberculosis infection. But X-Ray chest may shows opacity and calcification in healed and old tuberculous lesion in lungs and lymph nodes. If you have active Tuberculosis symptoms like evening rise in temperature, persistent cough with sputum and weight loss, we initially recommend sputum smear examination for Mycobacterium tuberculosis. However, it sometimes gives a negative result even in people with TB disease so a negative result cannot be relied upon. If it come negative, then we refer for Sputum culture. It is not necessary to have smear always positive. In sputum culture technique, growing of live TB bacteria in media in laboratory. This is a reliable method for detecting active TB disease as long as a suitable sample containing the TB bacteria can be obtained. Hope this helps. Please write back for further queries. Wishing you good health.