As far as the currently widely used third-generation double-primed sandwich method, enzyme-linked method, chemiluminescence method and other detection methods are concerned, the window period of AIDS can be shortened to 14 to 21 days. In this regard, the World Health Organization (WHO) clearly stated that the window period for AIDS is 14 to 21 days.

However, there may still be an error of a few ten thousandths, which cannot be detected, and this probability will become lower and lower.

Link: /question/20106110/answer/15725262

Source: Zhihu

Agreed with @高平陈. The window period of AIDS refers to the period from when the human body is infected with HIV to when the body produces antibodies. Since the concentration of HIV antibodies (HIV Ab) or antigen (HIV Ag) is extremely low at this time, it is difficult to detect; but during the window Individuals infected with HIV during this period are still contagious.

The following figure reflects the relationship between HIV detection (marker levels) and infection time. We will explain the window period of AIDS in two parts below: the window period of HIV antibodies (HIV Ab) and the window period of HIV antigen (HIV Ag).

(1) Window period of HIV antibodies (HIV Ab)

Theoretically, HIV antibodies will appear at the beginning of human infection with HIV, but the concentration at that time was extremely low and exceeded The scope of commonly used detection methods.

When the human body is infected with AIDS for about 1.5 weeks, it can be detected by the double-primer sandwich method (commonly known as the "gold standard method"). However, due to the low antibody concentration at this time, there is a certain error in the detection. When a human being is infected with HIV for 14 to 28 days, most detection methods including enzyme-linked method and double-origin sandwich method can obtain fairly accurate results. When a human is infected with HIV for 42 days, that is, about 6 weeks, the concentration of HIV antibodies in the human body reaches a peak, and then slowly decreases.

The current window period stipulated by the my country Centers for Disease Control and Prevention is 3 months.

(2) Window period of HIV antigen (HIV Ag)

Viral antigen detection is a more accurate method than antibody detection and can obtain quantitative results. As shown in the figure above, HIV Ag can reach its peak in about 4 weeks, and reliable results can be obtained one week earlier than HIV antibody.

However, since the content of AIDS antigen in the human body decreases rapidly after reaching its peak, and will drop below the detectable level in about 6 weeks, AIDS antigen detection is mostly used for scientific research analysis rather than clinical use.

The development of the concept of the AIDS window period

Since the discovery of AIDS in 1981, with the continuous advancement of detection methods, the definition of the AIDS window period has undergone many changes.

In the 1980s and 1990s, when AIDS research was still in its infancy, the American AIDS Research Foundation (American AIDS Research Foundation) led by Dr. Mathilde Krim, Ph.D. Foundation for aids research (AMFAR) proposed the concept of an AIDS window period of three months in early AIDS research. This was in view of the relatively backward detection methods at the time. This statement was adopted by the World Health Organization and was also compiled into Medical textbooks from around the world.

With the emergence of HIV antibody detection methods such as enzyme-linked method and double-primer sandwich method, the AIDS window period has been shortened to the most conservative 6 weeks when the HIV antibody peak occurs.

With the continuous development of AIDS testing technology, the window period of AIDS can be shortened to 14 years in terms of currently widely used third-generation double-primer sandwich method, enzyme-linked method, chemiluminescence method and other detection methods. ~21 days. In this regard, the World Health Organization (WHO) clearly stated that the window period for AIDS is 14 to 21 days.

Finally, we can conclude that there is a window period when HIV cannot be detected by conventional means.