Postexposure prophylaxis for human immunodeficiency virus infection after sexual or injection drug use exposure: Identification and characterization of the source of exposure

In a nonrandomized study of nonoccupational postexposure prophylaxis (PEP), a cross-sectional evaluation of subjects who were the source of human immu nodeficiency (HIV) exposure was performed to characterize partners of index subjects seeking nonoccupational PEP against HIV. Among 401 index subjects , 64 (16%) recruited a source subject. Those in a steady relationship and t hose who knew that the source subject was HIV antibody positive were more l ikely to recruit their source subject. Source subjects reported high rates of past (78%) and current (69%) antiretroviral use; 46% of those using anti retroviral drugs had detectable plasma HIV-1 RNA levels. Antiretroviral res istance was detected in many source subjects who reported any use of antire trovirals and was rare among source subjects who reported no history of ant iretroviral use. Clinicians often make treatment decisions on the basis of incomplete knowledge of the source subject's HIV status or antiretroviral t reatment history. The treatment history, particularly nonuse of a class of antiretroviral drugs, can be used to predict drug resistance.