The Impact of Human Immunodeficiency Virus Infection on Tuberculosis in Young Men in Seattle-King County, Washington* Susan R. Heckbert, M.D., Ph.D.; Ann Elarth, R.N.; and Charles M. Nolan, M.D. We conducted a population-based case-control study to determine the magnitude of the excess risk of tuberculosis in those infected with the human immunodeGciency virus (HIV) in Seattle-King County, Washington. Patients were 39 of the 54 cases of tuberculosis in white and in black (including Hispanic) men aged 20 through 49 reported to the Seattle-King County Department of Public Health between January 1986 and June 1988. Controls were 34 white and black men of similar age who had tuberculin testing as a condition of employment. Eleven (28 percent)

of the 39 patients with tuberculosis and 2 (6 percent) of the 34 controls tested positive for antibody to HIV (odds ratio adjusted for age and race 6.2; 95 percent confidence interval 1.2 to 31.9). Calculation of the etiologic fashion indicated that 24 percent of the tuberculosis cases in this population of young black and white men were attributable to concurrent HIV infection. (Chest 1992; 102:433-37)

1984, the long-term downward trend in tuberSince culosis morbidity in the United States has

tion at the time of diagnosis of tuberculosis. Based on accruing information about the natural history of HIV infection, the hypothesis offered to explain this association is that progressive immunosuppression due to HIV infection increases the risk of activation of preexisting dormant tuberculosis infection. 11 This hypothesis is supported by the findings of the study by Selwyn et al 12 of the occurrence of tuberculosis in 513 intravenous drug users in a methadone maintenance program. Eight new cases of tuberculosis occurred over a two-year follow-up period: seven in individuals who were HIV antibody positive and had a prior positive tuberculin skin test, and one in an HIV-positive individual without a prior positive tuberculin skin test. No tuberculosis occurred in HIVnegative individuals. In the state of Washington, the number of tuberculosis cases reported in 1985 rose 12 percent compared with 1984. Most of the increase was in the Seattle area and was limited to young men, from whom almost all AIDS cases have arisen in this region. Since these demographic data were compatible with an increase in tuberculosis cases due to HIV-related immunosuppression, we conducted a population-based case-control study to ascertain whether HIV infection is a risk factor for tuberculosis in young men in Seattle, to determine the magnitude of the excess risk, and to estimate the number and proportion of cases of tuberculosis in the population that were attributable to HIV infection.

changed. The number of tuberculosis cases reported each year from 1985 through 1988 fluctuated little, compared with an average rate of decline in case reporting of 6.7 percent per year from 1981 through 1984 1 and a general trend of gradual decline for many years previously. This change in tuberculosis morbidity, which has produced a cumulative excess of over 14,000 cases in the United States from 1985 through 1988, coincided with the upsurge of the acquired immune deficiency syndrome (AIDS) in this country.2 There is accumulating evidence of an association between infection with human immunodeficiency virus (HIV), the cause of AIDS, and tuberculosis. There are several published reports of case series with concurrent AIDS and tuberculosis, particularly from areas where AIDS is prevalent.3-R Cross-matching of AIDS and tuberculosis case registries from 43 states and 11 localities indicated that 4 percent ofall reported tuberculosis cases also appeared on AIDS registries. 2 Subsequent studies have suggested an association between tuberculosis and HIV infection, even in those in whom AIDS has not developed. Thirty-one percent of 71 patients with tuberculosis followed up at the Dade County, Florida, Public Health Department Tuberculosis Division,9 and 28 percent of 60 patients with tuberculosis followed up at the San Francisco General Hospital Tuberculosis Clinic lO had HIV infec-

=

=

AIDS acquired immune deficiency syndrome; UIV immunode6ciency virus

=human

METHODS

*From the Department of Epidemiolo~, School of Public Health and Community Medicine, University of \Vashington (Drs. Heckbert and Nolan), and the Tuberculosis Control Program, SeattleKing County Department of Public Health (Ms. Elarth, Dr. Nolan), Seattle. Manuscript received July 8; revision accepted November 25.

All white and black men (including those of Hispanic ethnicity) aged 20 through 49 reported to the Seattle-King County Department of Public Health as cases of tuberculosis from January 1986 through June 1988 were eligible for inclusion in the study. The diagnosis of tuberculosis was made in accordance with US Public CHEST I 102 I 2 I AUGUS"T, 1992

433

Table I-Characteristics of Tuberculosis Patients and Control Subjects

lhtal Age, yr 20-29 30-39 40-49

Patients n(%)

Control Subjects n(%)

39 (100)

34 (100)

12

13 9 12

14

Race \Vhite Black Hispanic Missing data Born outside United States Unemployed Risk factors for HIV infection Gay or bisexual Intravenous drug user Both gay and drug user Blood transfusion as only risk factor No risk factor identified

13

(31)

(36) (33)

(54) 14 (36) 4 (10)

21

5 (13) 26

(67)

7 7 2 3 20

(18) (18) (5) (8) (51)

(38) (26) (35)

26 (76) 5 (15) 2 (6) 1 (3) 1 (3) 3 (9) 9 2

(26) (6) o (0) 1 (3) 22 (65)

Health Service criteria. As re