PURIFIED PROTEIN DERIVATIVE TUBERCULIN AND DELAYED-TYPE HYPERSENSITIVITY SKIN TESTING IN MIGRANT FARM-WORKERS AT RISK FOR TUBERCULOSIS AND HIV COINFECTION

Objective: To assess the joint use of purified protein derivative (PPD ) and delayed-type hypersensitivity (DTH) antigens in screening indivi duals of unknown HIV serostatus for tuberculosis (TB) preventive thera py eligibility. Design: Population-based survey. Methods: A group of m igrant farm workers were screened for HIV and skin-tested with PPD, te tanus toxoid (TET), Candida albicans (CAN) and mumps (MUM) antigens by the Mantoux method. Anergy was defined as a less-than-or-equal-to 2 m m reaction to all four antigens. Eligibility for preventive therapy wa s defined as a reaction of greater-than-or-equal-to 5 mm to PPD among HIV-seropositive individuals, greater-than-or-equal-to 10 mm among HIV -seronegatives, or anergy. Results: A total of 253 out of 271 individu als had sufficient data for analysis. Of these, 15 (5%) were HIV-serop ositive; 183 (75%), 175 (72%) and 157 (65%) reacted to TET, CAN, and M UM, respectively, and 113 (47%) were eligible for preventive therapy [ 108 (44%) PPD-positive, five (2%) anergic]. Use of PPD alone was 95% s ensitive for detecting preventive therapy eligibility; PPD plus one DT H antigen was more sensitive (99%) but less specific (range, 69-85%); PPD plus two DTH antigens was most specific (CAN + MUM, 84%; TET + MUM , 93%; and TET + CAN, 100%). Conclusions: In this population with 5% H IV seroprevalence, testing for anergy did not significantly increase t he detection of preventive therapy eligibility. The use of two DTH ant igens is very sensitive and specific. These results support the recomm endation of joint PPD and anergy testing for the screening of HIV-sero positive individuals. Our data also suggest, however, that for individ uals whose HIV serostatus is unknown, anergy testing should be conside red as a screening tool only if the prevalence of anergy is expected t o exceed the prevalence of PPD positivity.