ELISA Test for HIV

ELISA Test for HIV


ELISA for diagnosis of HIV

What is HIV?

Human Immunodeficiency Virus ( HIV ) can be divided into two major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). HIV-1 is related to viruses found in chimpanzees and gorillas living in western Africa. HIV-2 is related to viruses found in sooty mangabeys. HIV-1 viruses may be further divided into groups. The HIV-1 group M viruses predominate and are responsible for the AIDS pandemic.

Since HIV was found in 1983, AIDS (Acquired Immunodeficiency Syndrome), a major infectious disease, has become a grave threat to human health. HIV is a type of virus called a retrovirus, which infects humans when it comes in contact with tissues by way of the vagina, anal area, mouth, or eyes, or through a break in the skin. AIDS is one of the five fatal diseases in the world. In some industrial countries, some antiretroviral therapy has been used to lower the spread and distribution to some extent, however, in many developing countries including African, Asian, and South American countries, there has been an increasing number of newly HIV infected crowd.

The stages from initial HIV infection until the final symptom of AIDS are described in three parts here. The primary stage of infection, which occurs weeks after infection of HIV, is often characterized by flu or some ailment. The chronic asymptomatic stage after infection often lasts eight to ten years on average. The final symptomatic stage, in which the immune system of the body has been suppressed and complications have developed, is called the acquired immunodeficiency syndrome (AIDS). The final symptoms are caused by the complications of AIDS, including severe loss of weight, cancers, or dementia (intellectual deterioration).

Symptoms and signs of HIV infections (AIDS)

The time from HIV infection to the development of AIDS varies among different persons. Usually, many HIV sufferers remain completely asymptomatic after as many as 20 years from the time of infection.
The most common symptoms of primary HIV infection are fever, aching muscles and joints, sore throat, and swollen glands (lymph nodes) in the neck.

It is unknown, however, why only some HIV sufferers develop these symptoms. It is also unknown whether or not these symptoms are related in any way to the future stage of AIDS. Regardless, infected people will become asymptomatic after this phase of primary infection. During the first weeks of infection when a patient may have symptoms of primary HIV infection, antibody testing may still be negative (the so-called window period). The early symptoms may not give enough evidence to define HIV infection; in that case, a special virus test of HIV is needed to be performed, such as a viral load test or the use of an assay that identifies HIV p24 antigen, for example, HIV-1 p24 ELISA Pair Set. Identifying and diagnosing individuals with primary infection is important to assure early access into care and to counsel them regarding the risk of transmitting to others. The latter is particularly important since patients with primary HIV infection have very high levels of virus throughout their body and are likely to be highly infectious. Once the patient enters the asymptomatic phase, infected individuals will know whether or not they are infected if a test for HIV antibodies is done.

After primary HIV infection, most individuals get into a period of no symptoms. During this stage, with a gradual decline of CD4 cells in the immune system, patients may develop the mild symptoms of HIV such as vaginal or oral candidiasis thrush (a fungal infection), fungal infections of the nails, a white brush-like border on the sides of tongue called hairy leukoplakia, chronic rashes, diarrhea, fatigue, and weight loss. Any of these symptoms indicate an urgent HIV test if not done yet. With a further decline in function of the immune system, patients may tend to suffer more severe complications including many more serious infections, severe weight loss, malignancies, and decline in mental function. From a practical perspective, most physicians regard symptoms of HIV sufferers as asymptomatic, mild symptoms, or severely symptomatic. In addition, many would characterize a patient's level of immunosuppression by the degree and type of symptoms they have as well as the CD4 cell level. The Centers for Disease Control and Prevention have defined the presence of a long list of specific diseases or the presence of less than 200 CD4 cells per mm3 as meeting a somewhat arbitrary definition of AIDS.

Diagnosis of HIV

The earliest test of HIV is a blood test in 1985. It was available to measure the antibodies to HIV which are the immune response to HIV. The most common method of diagnosis of HIV now is ELISA. If antibodies to HIV are found in ELISA, another technique is usually recommended to confirm the result, typically a test of western blot. However, antibodies to HIV typically develop within several weeks of infection. During this interval, if by the antibody test of ELISA or western blot, the result may show negative (the so called "window period"), while the virus of HIV does exist in a patient’s body. In that case, the diagnosis test can be made by detection of the presence of virus in the blood rather than the antibodies, such as tests for HIV RNA or p24 antigen, or just use a HIV-1 p24 ELISA Pair Set. Recently, a new test has been approved that measures both HIV antibodies and p24 antigen, shrinking the duration of the window period from infection to diagnosis.