It takes an average of six to 12 weeks for the human immunodeficiency virus, or HIV, to be detectable, according to Avert, although there have even been rare cases when HIV is not detected until as long as six months after infection. Anyone wishing to be tested should wait that long to be more certain of the outcome. There are several commonly used types of HIV tests.
ELISA Antibody Test
According to Avert, ELISA tests or enzyme-linked immunoabsorbent test (also known as enzyme immunoassay, or EIA) is the first form of HIV test to be widely employed. This form of testing is both accurate and relatively inexpensive compared to other tests. The San Francisco AIDS Foundation explains that ELISA tests can be performed on a blood sample. However, it is also possible to test saliva and urine. The test typically takes 3-1/2 to four hours to perform. The test looks for the presence of HIV antibodies in the sample and is typically performed twice to confirm results.
Rapid HIV Tests
Rapid HIV tests are similar to ELISA tests in the sense that they also look for HIV antibodies, according to the San Francisco AIDS Foundation. They take anywhere from 20 to 40 minutes to administer and are fairly accurate. Avert further explains that rapid HIV tests may use either saliva or blood. They do not require special training to administer. Because the test has a narrow margin for error, any positive results should be followed up with a second test to confirm accuracy.
Antigen Test (P24 Test)
According to Avert, HIV contains an antigen called protein P24 that triggers an antibody response. The antigen test, or P24 test, is geared toward detecting excessive levels of P24. But this is only possible during the early stage of infection, because as the infection progresses, the levels of P24 drop to undetectable levels. Therefore, the test is not typically used for general diagnosis.
Polymerase Chain Reaction Test
The polymerase chain reaction test is also called the viral load test, according to Avert. This form of test detects the genetic material of HIV rather than HIV antibodies. As such, a PCR test can detect the presence of the virus in the blood within two to three weeks of infection. The downside is that PCR tests are considerably more expensive and not as easily performed as the ELISA tests or rapid HIV tests.
About this Author
Joseph Pritchard graduated from Our Lady of Fatima Medical School with a medical degree. He has spent almost a decade studying humanity. Dr. Pritchard writes for the Examiner.com as the SF biology examiner and thoroughly enjoys sharing the knowledge he has accumulated.
