HIV Testing: Concept of HIV Testing

by admin on April 23, 2013

When the Human Immunodeficiency Virus enters a fresh victim it immediately starts the process of incubation. This process takes 2 days to 2 weeks; in some cases as long as 3 months. This actually is a fast replication process for the virus.

Concept of HIV Testing

The virus uses the host cells as resources to multiply as fast as possible. The replication process is faster in healthier and younger people because they have a faster metabolism. When the viruses increase in number, they are detected by the immune system of  the body.

The host body then starts the process to fight out the virus. The immune system develops antibodies to counter the antigens produced by the virus. In case of HIV the antigen is a protein called p24. This is the time when the first symptoms of HIV become apparent.

During this time the host body plasma, serum, saliva, discharges from different orifices or urine contains the antigen, antibodies,  and the RNA of the virus. If any of the three is found we can be sure that the individual is infected with HIV.

All HIV testing methods are aimed at detecting any one of the following three agents.

  • HIV antigens
  • HIV antibodies

To detect the agents in the test sample, it’s very important that they are present in sufficient quantity.


Types of HIV testing

  • HIV Antibody Test (ELISA)
  • HIV Antigen Test (p24 test)
  • PCR Test (Polymerase Chain Reaction Test)
  • Nucleic Acid Amplification Testing (NAAT)


HIV Test Window Period

The window period for each of these tests are different. The window period is the minimum time gap between infection time and testing time when a test can detect the presence of  HIV accurately. While conducting a test, the window period has to be taken into consideration to avoid false negatives. If we don’t allow sufficient time to elapse after the infection, then no test can detect the presence of the RNA, antigens or the antibodies even if HIV is present in the system.

Window time for the NAAT is 12 days. Within these 12 days HIV can sufficiently multiply in number so as to show its presence in the test. As the test uses the detection of the Nucleic Acid from the virus RNA, HIV must be present in sufficient numbers to show up in the test result. This is the fastest means of finding out an infection by HIV.

The window period for a PCR test is same as the NAAT as it uses the genetic material detection of HIV. Babies born to HIV positive mothers retain their mother’s antibodies for several months after birth. An antibody test always test HIV positive, hence inaccurate.  So, they are usually tested using a PCR test.

Window time for Antigen Test (p24 test) is approximately 16 days. By this time HIV produces sufficient antigens (p24 proteins) to show up conclusively in a test.

Window period for an Antibody Test (ELISA) is 25 days. By this time the host body can produce the HIV antibodies in sufficient quantity to reflect in an antibody test.

WARNING: The window period doesn’t indicate the capacity to infect others. Anybody with HIV present inside the body is quite capable of infecting others in case of intimate contact or needle sharing.

An early detection is the only hope to prevent a HIV infection from turning into AIDS.  As per HIV statistics, 1 individual in every 5 infected with HIV is unaware of the infection. These 20% not only pose a risk of infecting others but also they are in a great risk as far as their own well being is concerned.

To find out about different types of HIV/STD testing packages click here.

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