Robert G. Loudon

Thoracic tuberculosis: clinical aspects.

UBERCULOSIS was at the beginning of this century the most common single cause of death in the United States. It caused more deaths in 1900 (201 per 100,000) than heart disease or cancer and stroke put together.53 Tuberculosis is no longer the scourge that it was. The decline in deaths, disease, and infection caused by Mycobacterium tuberculosis represents the most important single contribution to health that has resulted from medical attention. It must be acknowledged that some portion of the improved situation about which we congratulate ourselves is the result of improving social conditions, but the most modest of phthisiologists can claim success resulting from his or her efforts. The changes and improvements continue. Further significant advances have been made over the last 10 years. The clinical picture of tuberculosis is markedly influenced by epidemiologic circumstances, and it is appropriate that roentgenologists, who have always had a particular interest in this disease and who have contributed so much toward the successes in the continuing fight, should be aware of what is going on in the epidemiologic, clinical, and laboratory worlds that live outside their lead-lined

Thoracic tuberculosis: Laboratory aspects

L ABORATORY SUPPORT is essential to the physician managing patients with tuberculosis. Patients on treatment may require laboratory monitoring-eg, with liver function tests-but the most important laboratory aspect to tuberculosis management is microbiologic. The mycobacteriology laboratory has four basic functions: (1) detection and isolation of mycobacteria, (2) identification of the species isolated, (3) drug-susceptibility testing, and (4) measurement of bacteriologic response to treatment.’ The diagnosis of tuberculosis should be confirmed bacteriologically whenever possible by demonstrating Mycobacterium tuberculosis on smear and culture. The techniques required to culture this organism are more demanding than those required to demonstrate the organism on smear. Growing the organism on culture has the advantage of allowing determination of the species, most important in regions where mycobacteria other 4 than M. tuberculosis are common. Culture of the organism is also a prerequisite for drug-susceptibility testing. It has been suggested that three levels of laboratory services should be available.’ Laboratories of level 1 are primarily concerned in collecting clinical specimens and transporting them to more specialized laboratories for further processing. They may also conduct smear examinations, interpret these, and provide the rapid information that this makes available to the clinician. Laboratories of the second level are equipped to set up specimens for culture, incubate these on appropriate media, and characterize any organisms that grow in terms of species, response to simple biochemical tests, and drug susceptibility to some of the antibiotics used in the treatment of tuberculosis. The third level of laboratory includes reference laboratories capa-