2-STEP TUBERCULIN SKIN TESTING IN HIV-INFECTED PERSONS IN UGANDA

Identifying persons infected with both human immunodeficiency virus (H IV) and Mycobacterium tuberculosis (MTB) is often difficult because of the reduced sensitivity of tuberculin skin testing in HIV-infected pe rsons. To determine the value of two-step tuberculin skin testing (TTS T) as a method of increasing the sensitivity of tuberculin skin testin g in HIV-infected persons, a consecutive sample of 58 HIV-infected per sons being screened for a TB preventive therapy trial in Uganda with a n initial purified protein derivative (PPD) response < 5 mm completed two-step tuberculin and candida skin testing. The mean change in PPD s ize between the two tests, placed a mean of 8 d apart, was +2.1 mm (SD 4.4 mm, range -4 to +16 mm). Seventeen subjects (29%) had a boosted r esponse (PPD1 < 5 and PPD2 greater than or equal to,5). In a multiple logistic regression model, boosted responses were independently associ ated with a CD4 count between 200 and 500 mu l(-1) (p = 0.02) and a hi gher body mass index (p = 0.05). TTST may be valuable in identifying M TB infection and in preventing misclassification of boosted responses as skin test conversions in HIV-infected persons, especially persons w ith CD4 counts between 200 and 500 mu l(-1) from areas with a high pre valence of MTB infection or from areas with a low prevalence of MTB in fection who have other risk factors for MTB infection.