The biological tests essential to HIV/AIDS diagnosis and treatment assess a number of important physical parameters. These tests, like all tests, have a margin of error. It is therefore necessary to provide patient counseling regarding: the meaning of specific test results, behavioral changes and the importance of follow-on confirmatory testing.

• HIV antibody
• CD4 t-cell
• Viral load
  

  HIV Antibody tests

The period between becoming infected and showing antibodies to HIV in the blood can range from 2 weeks to 6 months. During this period, a person can transmit the disease even though the antibodies cannot be detected in the blood. The most common tests in recent years have been ELISA, Western Blot and IFA.

Enzyme-linked immunosorbent assay (ELISA).

• Usually the first test used to detect infection with HIV, but can cause false positive results
  

Western blot.

• More difficult than the ELISA to perform and interpret accurately, but less likely to give a false-positives; used to confirm ELISA results.
  

Indirect fluorescent antibody (IFA)

• Detects antibodies made to fight an HIV infection; used to confirm ELISA results.
  

New rapid HIV tests are now on the market, that are quick, easy to do, and allow for point-of-care testing. There are 4 rapid HIV tests that have been approved:

• OraQuick Advance HIV-1/2 - results in 20 minutes (episodic false positive results)
• Uni-Gold Recombigen - results in 10 minutes
• Reveal G2 - results in 5 minutes
• Multispot HIV-1/HIV-2 - results in 15 minutes

Click here for indepth information from the CDC on Rapid HIV Testing. (A slide show, with step-by-step descriptions and photos of each step for all rapid HIV tests is one of the resources available at this link.

Be prepared to answer the following question, about HIV counseling, and communicating the meaning of rapid HIV test results.

If the rapid test is "negative", but the client has had a known or possible exposure within the last 3 months, there is no need to retest.

CD4 t-cell count

CD4 cells, also called T cells, are white blood cell (T-lymphocytes) that fight infection. HIV destroys CD4 cells, which depresses the immune system and increases the presence of the HIV virus in the blood.

Viral load

The viral load indicates the number of copies of HIV in the blood. A non-detectable result does not mean that there is no virus present; just that it was not detected. The newer versions of tests can now detect a load as low as 5 and as high as 1.5 million. A level of 55,000 requires antiretroviral treatment. Antiretroviral treatment is considered to be working if viral load drops by 90% within 8 weeks and continues to drop to less than 50 copies within 6 months. There are 2 different tests that give slightly different results. Therefore, when possible, people should be tested consistently with the same type of test.

• PCR (polymerase chain reaction)
• bDNA

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