Health Surveillance and Disease Management / Communicable Diseases / Tuberculosis
Manual for the Bacteriological Diagnosis of Tuberculosis:Standards and Technical Guidelines—Part 2, Cultures | |||||
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Full text (in Spanish, 114 pp, PDF, 2026 Kb; chapter headings translated below for user orientation) Editorial Team PAHO Links WHO Links Stop TB |
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Handbook produced especially for strengthening laboratory capacity in Latin America As was presented in the first part of this Manual, sputum-smear testing is the technique that supports tuberculosis control measures. With sputum-smear microscopy, the laboratory can start investigating a sample of patient lesions and look for the TB bacillus, detect it, evaluate the evolution of infectious cases, predict and endorse a cure for patients who successfully complete their treatment regimen, and identify those who fail in their treatment.
Cultures complement smear tests, since they can show viable bacilli present in limited quantity in a lesion sample, characterizing them so as to ascertain that it is indeed the TB bacillus and see if it is sensitive or resistant to TB drugs. Hence, the role of cultures is more important in scenarios with a median or low incidence of tuberculosis, with high levels of TB/HIV co-infection, and with a multiresistant medium or a high tuberculosis burden. Molecular techniques have been developed to achieve the same results of cultures with greater accuracy. These methods have still not managed to replace culture-dependent detection, identification, and sensitivity testing. A culture can be applied in laboratories with medium-level resources and maintains its position as main reference method by virtue of its precision. On the other hand, no immunological method has managed to equate the specificity of the culture in detecting and confirming the diagnosis of the disease caused by the TB bacillus; subsequently, on the basis of evidence to date, it is not reasonable to introduce such innovations into network tuberculosis diagnostic laboratories without ensuring beforehand coverage and quality with sputum-smear testing and cultures. Considering the prevalent epidemiological situation Latin America, the experience developed in the Region and the existing resources, it is appropriate to promote the value of cultures as the tool for tuberculosis control programs. A culture can improve program efficiency evaluations in treatment administration, optimize management of multidrug-resistant tuberculosis and that associated with HIV, and help make progress in controlling the disease where objectives established for infectious cases have been reached.
The situation analysis also leads to promoting quality assurance of cultures and ensuring access to this technique on the part of patients who can benefit from it. With this in mind, we have updated the standards for the identifying Mycobacterium tuberculosis through cultures. This second part of the Manual on Tuberculosis Bacteriology is devoted to laboratories that are assumed to already have ensured competition, quality, and biosafety in performing sputum-smear tests. Hence, the procedures presented here complement those described for carrying out sputum-smear microscopy in the first part of the Manual. These standards have taken into account those preceding them in Latin America (CEPANZOS Technical Notes No. 26, 27, 28 and 29/1988), those prepared by WHO (WHO/TB/98,258), and the experiences of the laboratories of the Region. They propose improving the technique implemented by the previous standard and offer a menu of methods for different scenarios, selected from those that have proved to contribute to TB diagnosis in Latin America, according to the evidence published. In addition, they provide details on procedures to increase the quality and biosafety in the workplace.
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