Denise Ford HIV-screening tests in state hospitals are usually referred to as “rapids” because they are fast and readily available. Positive “rapids” are usually sent on for a slightly more sophisticated test, Elisa (enzyme-linked immunoassay). It is customary to send two samples for each patient to minimise the chances of errors leading patients being given wrong results. Elisa tests involve adding the patient’s blood to a substance containing an enzyme that changes colour if antibodies to HIV are present. In doubtful or unusual cases samples are forwarded for a “Western blot” test. This expensive and time-consuming test involves filtering the patient’s blood for specific viral proteins. Another fairly new test is for “viral load”, the amount of virus in the blood. Not yet commonly used to diagnose HIV, viral-load tests are useful to see if anti- retroviral drugs are working, and how fast the infection is progressing. The test involves searching blood for HIV genetic material (RNA), and then amplifying it using a scientific procedure known as PCR (polymerase chain reaction). The test is very sensitive and can detect even minute quantities of the viral RNA. There are other tests that can be done on saliva and urine, but they are not commonly used because they are not as accurate as the blood tests.