A 24-year-old man is evaluated in an urgent care clinic for fever, cervical lymphadenopathy, and a faint erythematous rash on his chest and back. He reports condomless receptive anal sex with two male partners approximately 2 weeks prior. Tests for syphilis and mononucleosis are negative. The initial HIV-1/2 antigen-antibody immunoassay is positive, but the HIV-1/2 antibody differentiation immunoassay is negative.
What is the most appropriate next test to order?
Figure 1. Timing of Laboratory Tests After HIV Acquisition
This graphic shows conceptual timing of tests becoming positive following acquisition of HIV.
Illustration: David H. Spach, MD
Figure 2. Typical Pattern of Test Results in Persons with Acute HIV
This graphic shows a typical pattern (as highlighted by boxes with yellow borders) for persons with acute HIV using the Centers for Disease Control and Prevention and Association of Public Health Laboratories testing algorithm. The typical pattern with acute HIV consists of positive screening antigen-antibody test, negative differentiation assay, and positive HIV-1 nucleic acid test (NAT).
Source: (1) Centers for Disease Control and Prevention and Association of Public Health Laboratories. Laboratory Testing for the Diagnosis of HIV Infection: Updated Recommendations. Published June 27, 2014.(2) Centers for Disease Control and Prevention and Association of Public Health Laboratories. 2018 Quick reference guide: Recommended laboratory HIV testing algorithm for serum or plasma specimens. Published January 27, 2018.
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Question Last Updated
February 4th, 2025
February 4th, 2025
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