Therapeutic drug monitoring (TDM) in HIV disease may increase antiretroviral (ARV) efficacy by reducing toxicity, minimizing drug resistance, and managing drug-drug interactions. ARV measuring with current techniques (e.g. LC-MS-MS) is costly, labor intensive, and requires specialized equipment, thus limiting the application of TDM in selected clinical scenarios. The ARK LPV-Test™ is a new rapid, automated enzyme immunoassay (EIA) developed for determining plasma lopinavir (LPV) concentrations. Results using the EIA method were compared to those from a validated LC-MS-MS method.