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HIV/AIDS Online ELISA Test is one of thebestapplication to conduct free HIV/AIDS ELISA test online.we haveacertain number of questions and user needs to submit theproperanswers ,after completion our algorithm will calculate theresultand shows you,also we will give you the health tips andvaluablesuggestions.HIV tests are used to detect the presence of thehumanimmunodeficiency virus (HIV), the virus that causesacquiredimmunodeficiency syndrome (AIDS), in serum, saliva, orurine. Suchtests may detect antibodies, antigens, or RNA.The window period is the time from infection until a test candetectany change. The average window period with HIV-1 antibodytests is25 days for subtype B. Antigen testing cuts the windowperiod toapproximately 16 days and NAT (Nucleic Acid Testing)further reducesthis period to 12 days.[2]Performance of medical tests is often described in terms of:sensitivity: The percentage of the results that will bepositivewhen HIV is presentspecificity: The percentage of the results that will benegativewhen HIV is not present.All diagnostic tests have limitations, and sometimes their usemayproduce erroneous or questionable results.False positive: The test incorrectly indicates that HIVispresent in a non-infected person.False negative: The test incorrectly indicates that HIV is absentinan infected person.Nonspecific reactions, hypergammaglobulinemia, or the presenceofantibodies directed to other infectious agents that maybeantigenically similar to HIV can produce false positiveresults.Autoimmune diseases, such as systemic lupus erythematosus,havealso rarely caused false positive results. Most falsenegativeresults are due to the window period.ELISAThe enzyme-linked immunosorbent assay (ELISA), or enzymeimmunoassay(EIA), was the first screening test commonly employedfor HIV. Ithas a high sensitivity.In an ELISA test, a person's serum is diluted 400-foldandapplied to a plate to which HIV antigens have been attached.Ifantibodies to HIV are present in the serum, they may bind totheseHIV antigens. The plate is then washed to remove allothercomponents of the serum. A specially prepared "secondaryantibody"— an antibody that binds to human antibodies — is thenapplied tothe plate, followed by another wash. This secondaryantibody ischemically linked in advance to an enzyme. Thus theplate willcontain enzyme in proportion to the amount of secondaryantibodybound to the plate. A substrate for the enzyme is applied,andcatalysis by the enzyme leads to a change in color orfluorescence.ELISA results are reported as a number; the mostcontroversialaspect of this test is determining the "cut-off" pointbetween apositive and negative result.Source :https://en.wikipedia.org/wiki/Diagnosis_of_HIV/AIDS