INSTABILITY OF DELAYED-TYPE HYPERSENSITIVITY SKIN-TEST ANERGY IN HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION

Objective: To evaluate stability of delayed-type hypersensitivity (DTH ) skin test over time in human immunodeficiency virus (HIV)-seropositi ve and HIV-seronegative injecting drug users. Method: A community-base d cohort of injecting drug users who had serial skin testing with puri fied protein derivative tuberculin, mumps, and Candida albicans antige n. Delayed-type hypersensitivity anergy was defined as a skin test res ult of less than 3 mm for all three antigens; DTH positivity was a ski n test result of 3 mm or greater for at least one antigen (Centers for Disease Control and Prevention, Atlanta, Ga, 1993). Results: At basel ine, 36% of HIV-seropositive subjects (n=401) were anergic as compared with 14% of HIV-seronegative subjects (n=552; P<.001). During follow- up, fewer HIV-seropositive subjects remained DTH positive (42%) and mo re remained anergic (19%) than of HIV-seronegative subjects (67% and 7 %, respectively). Twenty-four percent of HIV-seropositive subjects who were initially DTH positive became anergic as compared with 15.3% of the HIV-seronegative subjects. However, the proportion changing from a nergy to DTH positivity was greater among HIV-seropositive subjects (1 5%) than HIV-seronegative subjects (12%). In comparison to those who r emained DTH positive, HIV-seropositive subjects with CD4 cell counts o f less than 0.50 X 10(9)/L (odds ratio=6.4) and less than 0.35 X 10(9) /L (odds ratio=11.2) were more likely to remain anergic than those who had CD4 cell counts above 0.50 X 10(9)/L or were HIV seronegative. Co nclusions: Although the prevalence and incidence DTH anergy were highe r in HIV-seropositive subjects, high rates of change in DTH status occ urred in both directions. This suggests that instability of DTH skin t esting is substantial and only partially dependent on HIV status. Alth ough a single test may be an unreliable indicator of HIV-induced immun osuppression, two consecutive anergic readings were strongly associate d with a CD4 cell count below 0.50 X 10(9)/L and particularly below 0. 35 X 10(9)/L. For determining false negativity of tuberculin tests, pe rsistent DTH anergy is more reliable than a single test among HIV-sero positive injecting drug users. Anergy testing appears to be unnecessar y with CD4 cell counts greater than 0.50 X 10(9)/L.