system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A patient comes to hospital with a history of sore throat, diarrhea and sexual contact 2 weeks before. The best investigation to rule out HIV is:
assistant
The correct answer is  Ans. is 'a' i.e., p. 24 antigen assay (Ref: Ananthanarayan, 9th/e, p. 577 - 578 and 8th/e, p. 576)* p24 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.Remember: Nucleic acid tests (RT - PCR, BONA, PCR) are the earliest test to become positive (even before p24 antigen detection).TestPositive after infectionNucleic acid test12 daysp24 antigen test16 daysAntibodies test22 days