a medical history that includes questions about symptoms, possible exposure to someone with infectious tuberculosis, past history of the disease, country of origin, age, place of work, and other medical conditions such as HIV infection associated with higher risk of tuberculosis;
a physical examination;
a chest radiograph to look for abnormalities suggestive of active pulmonary tuberculosis (or signs of infection or past tuberculosis that might warrant treatment); and
laboratory tests for evaluation of sputum samples.13
Laboratory samples are usually first assessed with a smear that can be quickly processed to provide a report within 24 hours. Smears allow the identification of mycobacteria but not the identification of M. tuberculosis specifically. A follow-up culture will produce more accurate and specific information, but even with the latest technology, reports will generally not be available for several days. Tests to evaluate drug susceptibility may be done sequentially after culture confirmation of disease, thus adding further to delays in starting appropriate treatment.
Molecular analysis (DNA fingerprinting) compares isolates of M. tuberculosis recovered from different individuals. Such analysis can help establish a chain of transmission that links new cases of active disease to source cases. It sometimes allows cases of active tuberculosis among workers to be more accurately linked to previously identified cases in the community or the workplace than was previously possible. The establishment of such links can help guide tuberculosis control efforts. As discussed in Chapter 5, uncertainty about the origins of tuberculosis infection and disease among health care and other workers contributes to uncertainty about the value of regulations in the control of occupational exposure. Some health care worker groups with the high rates of positive skin test results come from populations with high rates of active tuberculosis in the community (Appendix C). Current tests cannot identify the source of tuberculosis infection.
Failures to promptly identify, isolate, and treat those with diagnosed or suspected infectious tuberculosis are major weak points in programs to prevent occupational exposure to the disease. Unfortunately, community-and workplace-based efforts to improve timely and accurate diagnosis of
A tuberculin skin test is optional. Even if it is negative, it does not rule out the disease, especially in someone with symptoms or risk factors such as HIV infection or recent (less than 10 weeks) exposure to a person with infectious tuberculosis. For those with possible nonpulmonary tuberculosis, testing may involve blood, bone marrow, and other tissue.