Prevalence of anergy among hospitalized drug users in southern Tehran

Background: Prevention strategies rely heavily on the use of tuberculin test to identify persons harbouring tuberculosis. Anergy undermines these strategies in persons at the highest risk for tuberculosis infection and subsequent active disease. Materials and methods: Patients with a history of drug use for more than 6 month who were admitted in Loghman Hakim and Imam Hussein hospitals between January 2005 and October 2006 were recruited. The tuberculin PPD, tetanus toxoid and candida skin tests were performed and read at 48–72 hours. Anergy was defined as the absence of reaction to either any of the three antigens or by ?2 mm induration in response to all of tetanus, candida, and tuberculin antigens. Results: A total of 221 patients (216 male, mean age 43.5 ± 14.3 years) were studied. Tuberculin skin test results showed that 87 subjects (39.4%) tested positive for TB reactivity. Reactivity to tetanus and candida antigens were observed in 214 (96.8%) and 197 (89.1%), respectively. Skin test anergy was found in 5 subjects (2.3%). Anergic cases were all male, HIV seronegative and opium users. Conclusion: Skin test anergy is uncommon among drug users and the PPD skin test may be reliably used for the identification of latent TB infection in the population.