Tuberculosis (TB)

The five elements of DOTS


Element 2

Case detection through quality-assured bacteriology

Bacteriology for diagnosis. Bacteriology remains the recommended method of TB case detection, first using sputum smear microscopy and then culture and drug susceptibility testing (DST), as indicated below.

Strengthened laboratory network. A wide network of properly equipped laboratories with trained personnel is necessary to ensure access to quality-assured sputum smear microscopy. This is likely to require additional investments in the laboratory network in many countries. In addition, every country should have a well-resourced and fully functioning national reference laboratory.

The laboratory network should be based on the following principles:

  • adoption of national standards in accordance with international guidelines;
  • decentralization of diagnostic services, with high proficiency levels maintained;
  • communication among members at various levels of the network; and
  • functioning internal and external quality management, including supervision.

Culture and DST services should be introduced, in a phased manner, at appropriate referral levels of the health system. Their functions should include diagnosis of sputum smear-negative TB, diagnosis of TB among HIV-positive adults and children, diagnosis and monitoring of response to treatment of MDR-TB, and testing related to periodic surveys of the prevalence of drug resistance. Maintaining the quality of the laboratory network depends on regular training, supervision and support, and motivation of laboratory staff. Best use should be made of existing public and private laboratories.

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