Testing in the window period

Polymerase chain reaction

The fist marker for HIV infection that can be detected is the presence of HIV-RNA which can be found as early as 11 days after transmission. Even though polymerase chain reaction (PCR) tests can be used as an additional test for helping to detect HIV-infections during the window period, there are several reasons why a PCR test is not suitable alone for primary diagnostics. It is expensive, labor intensive and it needs special facilities. In addition, because of its sensitivity and specificity, all preliminary positive PCR results must be confirmed with HIV-antibody tests to confirm infection. PCR tests are mainly used to monitor the progression of infection and treatment outcomes. In addition, it is used in the diagnosis of HIV infection in infants born to mothers living with HIV.

Antibody / p24 Antigen combo assay

These assays detect both HIV antibodies and antigens. The mean time between HIV-infection to the possibility of detecting the HIV p24 antigen is 16 days. Because the HIV p24 antigen can be detected in plasma in only approximately 50% of HIV-infected individuals, these tests cannot be used alone for primary diagnostics. As in the case of PCR, all preliminary p24 antigen positive results must be confirmed with HIV-antibody test to confirm the infection.