AMERICAN JOURNAL or EPIDEMIOLOGY

Copyright © 1979 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved

Vol. 109, No. 2 Printed in U.S-A.

EXTRAPULMONARY TUBERCULOSIS IN THE UNITED STATES1 LAURENCE S. FARER, ANTHONY M. LOWELL AND MARION P. MEADOR Farer, L. S., A. M. Lowell and M. P. Meador (CDC, Atlanta, GA 30333). Extrapulmonary tuberculosis In the United States. Am J Epidemiol 109: 205-217, 1979. In recent years, the decrease in reported tuberculosis In the United States has been due almost entirely to a drop In the number of cases of pulmonary disease. There has been little change in the average number of extrapulmonary cases reported. A retrospective survey of extrapulmonary tuberculosis has shown that It differs from pulmonary tuberculosis with regard to sex and race distribution, diagnosing physician's specialty and proportion of cases bacterlologlcally confirmed. There Is variation within extrapulmonary cases according to specific anatomic site with regard to the above characteristics as well as age distribution. These epldemiologic differences In tuberculosis of different sites are unexplained. communicable diseases; epidemiologic methods; retrospective studies; statistics; tuberculosis

Tuberculosis in organs other than the lung has been observed for centuries but has not always been recognized as tuberculosis. The protean nature of tuberculosis led ancient practitioners of medicine to1 divide phthisis (consumption) into many supposedly separate diseases. Throughout history, extrapulmonary tuberculosis has been referred to by many names, such as Pott's disease, lupus vulgaris and scrofula, describing what is now known to be tuberculosis of the spine, the skin, and the cervical lymph nodes. Scrofula was well recognized by the 17th century in Europe, where it was Received for publication April 3, 1978, and in final form June 26, 1978. 1 From the Center for Disease Control, Atlanta. Reprint requests to Technical Information Services, Bureau of State Services, Center for Disease Control, Atlanta, GA 30333. The authors acknowledge the generous assistance of cooperating state and local health departments in making available their facilities and records for this study. Special thanks are due to Ms. Barbara Woolf for preparing the statistical sample, Ms. Sandra Jewell for statistical consultation, Ms. Helen Costello for assistance with computer programming, and to Ms. Mary C. Shearin for manuscript assistance.

called the "King's Evil" because of the belief that it could be cured by the laying on of hands by the sovereign; Charles II of England is reputed to have applied the "Royal Touch" to the scrofulous 90,798 times. Not until the 19th century when pathology emerged as a science was the unity of the tubercle recognized. Following the discovery of the tubercle bacillus in 1882 by Robert Koch, rapid advances in bacteriologic diagnostic techniques provided the scientific basis for the current view of tuberculosis as a systemic infectious disease with varying clinical manifestations (1). In modern times, in the United States, all forms of tuberculosis, both pulmonary and extrapulmonary, have been reportable. It was observed in the early 1960s that although the number of reported pulmonary cases was declining steadily, the number of extrapulmonary cases appeared to be leveling off. In recent years the decrease in reported tuberculosis has been accounted for almost entirely by a drop in pulmonary cases; there has been little change in the average number of extrapulmonary cases reported by the

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206 YEAR

FARER, LOWELL AND MEADOR 1964

1965

1966

1967

1968

1969 1970

1971

1972

1973

1974

1975

1976

- 50,000

50,000 -

Pulmonary Cases

> 40,000

-40,000

C3

30.000 -

-30,000

20,000 -

- 20,000

10,000-

Extrapulmonary Cases

-10,000

1

FIGURE 1. Pulmonary and extrapulmonary tuberculosis cases, United States, 1964-1976. (*Criteria for counting reported cases changed in 1975.)

states. The incidence of extrapulmonary tuberculosis has remained around 4000 cases per year, ranging from a low of 3650 in 1969 to a high of 4589 in 1975. Because of this phenomenon, the proportion of all reported cases which are extrapulmonary has almost doubled, from 7.8 per cent in 1964 to 13.7 per cent in 1976 (figures 1 and 2). The proportion of extrapulmonary cases varies widely among the states and does not appear to be completely random. There appears to be an inverse relationship between the tuberculosis case rate and the proportion of cases reported as extrapulmonary (r = —.37, p < .05). Generally, in states with higher tuberculosis rates, the per cent of cases which are extrapulmonary tends to be lower;

in states with lower rates, the per cent of cases which are extrapulmonary tends to be higher (figure 3). Prior to 1975, information on extrapulmonary tuberculosis for the country was limited to the total number of cases. No details were available on such factors as age, race, sex, anatomic site, or bacteriologic status. With the steady rise in the proportion of extrapulmonary disease, it was realized that additional information would be needed on specific characteristics of extrapulmonary cases in order to explore the factors which might account for the lack of decline in these forms of tuberculosis. Therefore, in 1975, detailed information on extrapulmonary cases was added to the data collection forms submitted to the Center for Disease

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EXTRAPULMONARY TUBERCULOSIS IN THE USA YEAR

207

1964 | 1965 | 1966 | 1967 | 1968 | 1969 | 1970 | 1971 | 1972 | 1973 | 1974 | 1975 | 1976

30.0

30.0

Pulmonary Case Rate