<P> HIV tests are used to detect the presence of the human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS), in serum, saliva, or urine . Such tests may detect antibodies, antigens, or RNA . </P> <P> AIDS is diagnosed separately from HIV . </P> <P> The window period is the time from infection until a test can detect any change . The average window period with HIV - 1 antibody tests is 25 days for subtype B. Antigen testing cuts the window period to approximately 16 days and nucleic acid testing (NAT) further reduces this period to 12 days . </P> <P> Performance of medical tests is often described in terms of: </P>

Which of the following signs needs to be present to diagnose aids