Decisions about when and how to use NAA tests for TB diagnosis should be individualized. NAA tests cannot replace clinical judgment or be relied on as the only guide for therapy or isolation practices. The tests may enhance diagnostic certainty, but should be interpreted in a clinical context and on the basis of local laboratory performance. Follow-up bacteriologic examinations are important for assessing the patient s infectiousness and response to therapy. At a minimum, specimens should be obtained at monthly intervals until the culture results convert to negative.
Culture conversion is the most important objective measure of response to treatment.
Laboratories should report positive smears and positive cultures within 24 hours by telephone or fax to the primary health care provider. Follow-up results may be reported by mail. For all patients, the initial M. tuberculosis isolate should be tested for drug resistance. It is crucial to identify drug resistance as early as possible in order to ensure appropriate treatment. Susceptibility results from laboratories should be promptly forwarded to the health department.