A person has unprotected sex 3 weeks back. To rule out HIV infection the best test is-

Ans. is 'a' i.e., p24 antigen assay Laboratory diagnosis of HIV infectiono 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 'gold 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 patient's lymphocyte with uninfected lymphocytes in the presence of IL-2# Not suitable as a routine diagnostic procedure.In infected individual HIV can be isolated fromo Bloodo Lymphocyteso Semeno Cervical secretionso Salivao Tearso Urineo Breast milk