Newer diagnostic techniques for tuberculosis

Early confirmation of the diagnosis of tuberculosis is a challenging problem specially in case of paucibacillary and extra-pulmonary forms. Conventional methods available for diagnosis namely, tuberculin test, radiological examination and other imaging methods and sputum smear microscopy have their own limitations. Histopathology is characteristic but there could be problems to get representative specimen, and non specific features. Immunology is often not conclusive as antibodies and delayed type hypersensitivity response persist for a long time after the subsidence of sub-clinical or clinical disease. Sputum smear microscopy requires 10,000 to 1,00,000 organisms/ml and acid fast bacilli (AFB) could be any pathogenic or saprophytic mycobacteria. Smear microscopy can be made much more convenient by using various fluorochrome dyes such as auramine and rhodamine1. Accurate identification of Mycobacterium tuberculosis through culture is presently the yardstick for diagnosis, but the time required and frequent negative results in paucibacillary specimens are important limitations. During the last two decades, several methods for achieving early growth of M.tuberculosis have been developed2. Some of the important methods are: (i) BACTEC system: This assay system developed by Becton Dickinson, is based on generation o