<prompt> Test used for diagnosis of HIV infection during window period -p-24 antigenp-18 antigengp-120 antigengp-41 antigen  <response>: Ans. is a i.e., p-24 antigen P-24 antigen is the earliest virus marker to appear in blood and is the one tested for. It may be detectable in blood after about 2 weeks.Laboratory diagnosis of HIV infection Laboratory diagnosis is made by:A Antibody detection It is the most common method used for diagnosis of HIV infection. ELISA is the most sensitive test and therefore is the serening test of choice. Western blot is the most specific Confirmatory test and therefore is the 4gold standard for diagnosis, Antibodies test usually become positive 22 days after the infection.B Detection of HIV nucleic acid or antigen p24 antigen detection by ELISA can be done 16 days after infection earlier than antibody detection. Nucleic acid detection tests are the earliest to become positive 12 days after infection. Most commonly used test is reverse transcriptase PCR, RT-PCR. Other methods used are DNA-PCR, RNA-PCR, RNA- bDNA branched DNA, and RNA-NASBA nuclei acid sequenced based assay.C Virus isolation Co-cultivation of the patients lymphocyte with uninfected lymphocytes in the presence of IL-2 Not suitable as a routine diagnostic procedure.In infected individual HIV can be isolated from : Blood Semen Saliva Urine Lymphocytes Cervical secretions Tears Breast milk 