This test uses Quantitative Real-Time Reverse Transcription Polymerase Chain Reaction (RT-PCR) to measure the amount of Human Immunodeficiency Virus type 2 (HIV-2) RNA in serum or plasma blood samples. The result is expressed as the number of viral copies per milliliter (copies/mL) or International Units (IU/mL), and is the primary standard for assessing viral load and evaluating the effectiveness of Antiretroviral Therapy (ART).