Reports on HIV/AIDS: 1990

SEPTEMBER 21, 1990, MMWR, Vol. 39, No. 37, pp. 638-639, 645-646
suggest that HIV infection can depress tuberculin reactions before signs and symptoms develop. Because additional diagnostic studies (e.g., CD4 cell counts, anergy
test panels, p-2-microglobulin, p-24 antigen levels, or other measures of the stage of
HIV disease) were not done in these women, the investigators could not determine
whether nonreactivity to tuberculin was associated with more advanced HIV disease.
However, a recent study in Florida of patients who were reported as having both
TB and acquired immunodeficiency syndrome (AIDS) indicated that the probability of
tuberculin anergy was inversely related to the interval between diagnosis of TB and
diagnosis of AIDS (6). Tuberculin skin testing in asymptomatic HIV-seropositive and
HIV-seronegative intravenous-drug users in Switzerland and in prisoners in Italy also
detected lower rates of PPD reactivity among those with HIV infection (7,8). In Italy,
the mean CD4 count for those with HIV infection was 569/mm3, and the CD4:CD8 ratio
was 0.6:1.0; both of these values were lower than normal. Thus, the reliability of
tuberculin skin tests in screening for TB and tuberculous infection may be lower in
HIV-infected persons, especially those with low CD4 counts.
An important finding in Uganda is that the prior administration of BCG appears to
maintain tuberculin reactivity at higher levels than in persons with. "natural" mycobacterial infection. Therefore, prior BCG vaccination complicates the interpretation of
skin test results and decisions about preventive therapy (9).
The Advisory Committee for Elimination of Tuberculosis and the American
Thoracic Society recommend that tuberculin reactions >5 mm be considered positive
in HIV-seropositive persons (regardless of BCG vaccination status) and that such
persons be considered for isoniazid prophylaxis (2). Based on the data from Uganda
and the other sources cited above, persons with HIV infection and tuberculin skin test
reaction sizes <5 mm who have evidence of immunosuppression (e.g., CD4 count
<400/mm3 and/or anergy to other delayed-type hypersensitivity skin test antigens)
may also need to be considered for isoniazid preventive therapy; such consideration
should also be based on individual clinical and epidemiologic assessments of the
likelihood of M. tuberculosis infection.
The problem of HIV-related tuberculin anergy among persons in the United States
requires further evaluation, and a more sensitive and specific method for diagnosing
tuberculous infection among immunosuppressed persons is needed. Studies of the
usefulness of CD4 counts or other laboratory parameters in predicting anergy and of
the optimal method of determining anergy (e.g., single antigen or anergy panel) are
particularly important. CDC will be developing more specific recommendations on
anergy testing and the administration of preventive therapy for immunosuppressed
persons.
References
1. Selwyn PA, Hartel D, Lewis VA, et al. A prospective study of the risk of tuberculosis among
intravenous drug users with human immunodeficiency virus infection. N Engl J Med 1989;
320:545-50.
2. CDC. Tuberculosis and human immunodeficiency virus infection: recommendations of the
Advisory Committee for the Elimination of Tuberculosis (ACET). MMWR 1989;38:236-8,
243-50.
3. Rieder HL, Cauthen GM, Kelly GD, Bloch AB, Snider DE. Tuberculosis in the United States.
JAMA 1989;262:385-9.
4. Styblo K. The global aspects of tuberculosis and HIV infection. Bull Int Union Tuberc Lung Dis
1990;65:28-32.
5. Goodgame RW. AIDS in Uganda-clinical and social features. N EngI J Med 1990;323:383-9.

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