Diagnostic methods for tuberculosis

Tuberculosis (TB) is a major public health problem especially in the third world countries. In India, it is estimated that at present there may be approximately 10 million persons suffering from radiologically evident pulmonary TB of whom about 2.5 million would be sputum positive. The number of deaths due to tuberculosis is estimated to be approximately 5,000,000 every year. Definitive diagnosis of tuberculosis depends on smear examination and culture of appropriate biological fluids. Only up to 50% of pulmonary and 25% of extrapulmonary TB are diagnosed by smear examination. Traditional culture methods take around 6 weeks before the diagnosis can be established. Chemotherapy for tuberculosis is prolonged, expensive and not free from serious side effects. If the diagnosis of TB is delayed, it leads to increases morbidity and in some cases mortality (e.g. tuberculous meningitis). Often the clinicians have to start therapy empirically. There is a great need, therefore, for tests which are highly sensitive and specific as well as rapid.