Objectives
  • Disseminate info on TB in India
  • Improve care of TB patients in India
  • Enable doctors and NGO's interested in TB control to interact

Diagnosis of Tuberculosis

Microscopy in tuberculosis

The diagnosis of tuberculosis is confirmed on the basis of the demonstration of tubercle bacilli in sputum or any other pathological material. The national Tuberculosis programme of India introduced in 1962 aimed at giving priority to sputum positive cases to break the chain of transmission.
Smear examination is believed to be simple,cheap,quick and the most practicable and effective case finding tool for most developing countries.Examination is by Ziehl-Neelsen(ZN) staining method or in well equipped laboratories by fluorescence microscopy; The disadvantages of smear microscopy are:
  1. Scanty positives cannot be detected
  2. It cannot be determined whether the bacilli are dead or living
  3. Information the type of bacilli, their drug sensitivity pattern cannot be assessed
The microscopic examination of sputum smears stained by ZN method can detect bacilli when they are of the order of 104per ml of sputum.Sputum microscopy has been shown to have a specificity of 96.5 % and sensitivity of 34.9%.Sputum smear microscopy is less sensitive in HIV associated tuberculosis. The paucibacillary cases can be detected by culture in Lowensten Jensen or Middlebrook's media. The method is also useful for finding out the type of bacillus, the viability and drug sensitivity. The drawback of culture is that it takes about 6-8 weeks to get the result.result. Rapid radiometric tests have been introduced to overcome this problem.
In developing countries culture facilities are available only in limited number of laboratories.
Sputum smear is the most widely used diagnostic test but it demands skilled and very patient technician and supplies of slides and stains.