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THE VALUE OF SKIN TESTING IN HIV-INFECTED PATIENTS.

Delayed-type hypersensitivity skin testing is done in HIV-infected patients to assess cellular immunity and determine tuberculin reactivity. Three studies add to our understanding of these tests.

The first study evaluated 889 HIV-positive U.S. Air Force personnel with skin tests for tuberculin and four control antigens (mumps, candida, tetanus toxoid, and trichophyton). Anergy correlated with CD4 count; for example, only 2 percent of patients with CD4 counts above 800 per cubic millimeter were anergic, versus 59 percent of patients with counts below 200. Tetanus toxoid had the strongest correlation with CD4 count, and trichophyton had the weakest correlation. After controlling for CD4 count, anergy remained an independent predictor of progression to AIDS.

The second study found the same inverse correlation between delayed-hypersensitivity response and CD4-cell count in 1171 HIV-positive patients from six U.S. centers. In addition, the prevalence of tuberculin reactivity directly correlated with CD4 count, ranging from 8 percent of patients with counts above 600 to 1 percent of patients with counts below 200. This confirms that tuberculin testing should be performed early in the course of HIV infection, before anergy develops.

Finally, a study in Spain, where tuberculosis is prevalent, assessed the risk for TB in 347 HIV-infected patients who had not received isoniazid prophylaxis. After about 2 years, the incidence of active TB was 28 percent in the 84 patients with an initial positive tuberculin test, 18 percent in the 112 patients who were initially anergic, and 13 percent in the 151 initially tuberculin-negative patients who were not anergic. These high rates suggest a substantial risk of both reactivated latent TB and new TB infection among HIV-positive patients living in high-prevalence areas. An editorialist notes that all three patient groups are candidates for isoniazid prophylaxis in such areas.

— ASB

Published in Journal Watch General Medicine August 13, 1993

Citation(s):

Kornbluth RS; McCutchan JA. Skin test responses as predictors of tuberculous infection and of progression in HIV-infected persons. Ann Intern Med 1993 Aug 1 119 241-243.

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Moreno S et al. Risk for developing tuberculosis among anergic patients infected with HIV. Ann Intern Med 1993 Aug 1 119 194-198.

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• Medline abstract (Free)

Markowitz N et al. Tuberculin and anergy testing in HIV-seropositive and HIV-seronegative persons. Ann Intern Med 1993 Aug 1 119 185-193.

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• Medline abstract (Free)

Blatt SP et al. Delayed-type hypersensitivity skin testing predicts progression to AIDS in HIV-infected patients. Ann Intern Med 1993 Aug 1 119 177-184.

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• Medline abstract (Free)

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