Description

HIV/AIDS Online ELISA Test is one of the bestapplication to conduct free HIV/AIDS ELISA test online.we have acertain number of questions and user needs to submit the properanswers ,after completion our algorithm will calculate the resultand shows you,also we will give you the health tips and valuablesuggestions.
HIV tests are used to detect the presence of the humanimmunodeficiency virus (HIV), the virus that causes acquiredimmunodeficiency syndrome (AIDS), in serum, saliva, or urine. Suchtests may detect antibodies, antigens, or RNA.
The window period is the time from infection until a test candetect any change. The average window period with HIV-1 antibodytests is 25 days for subtype B. Antigen testing cuts the windowperiod to approximately 16 days and NAT (Nucleic Acid Testing)further reduces this period to 12 days.[2]

Performance of medical tests is often described in terms of:

sensitivity: The percentage of the results that will be positivewhen HIV is present
specificity: The percentage of the results that will be negativewhen HIV is not present.
All diagnostic tests have limitations, and sometimes their use mayproduce erroneous or questionable results.

False positive: The test incorrectly indicates that HIV ispresent in a non-infected person.
False negative: The test incorrectly indicates that HIV is absentin an infected person.
Nonspecific reactions, hypergammaglobulinemia, or the presence ofantibodies directed to other infectious agents that may beantigenically similar to HIV can produce false positive results.Autoimmune diseases, such as systemic lupus erythematosus, havealso rarely caused false positive results. Most false negativeresults are due to the window period.
ELISA
The enzyme-linked immunosorbent assay (ELISA), or enzymeimmunoassay (EIA), was the first screening test commonly employedfor HIV. It has a high sensitivity.

In an ELISA test, a person's serum is diluted 400-fold andapplied to a plate to which HIV antigens have been attached. Ifantibodies to HIV are present in the serum, they may bind to theseHIV antigens. The plate is then washed to remove all othercomponents of the serum. A specially prepared "secondary antibody"— an antibody that binds to human antibodies — is then applied tothe plate, followed by another wash. This secondary antibody ischemically linked in advance to an enzyme. Thus the plate willcontain enzyme in proportion to the amount of secondary antibodybound to the plate. A substrate for the enzyme is applied, andcatalysis by the enzyme leads to a change in color or fluorescence.ELISA results are reported as a number; the most controversialaspect of this test is determining the "cut-off" point between apositive and negative result.

Source :https://en.wikipedia.org/wiki/Diagnosis_of_HIV/AIDS