<s>[INST] context: Reverse transcriptase (RT) PCR for HIV RNA (d) has recently been shown to be the most valuable test for diagnosis of acute HIV infection (acute retroviral syndrome) during the window period before antibodies can be detected. This qualitative test for detection of HIV virions is positive at the time symptoms of acute infection appear, as early as 7 days post infection; the test is also positive in asymptomatic individuals and is used to screen donated blood. The test for HIV p24 antigen (c) is the next to become positive, 17 to 38 days after infection. Antibodies appear last at 21 to 42 days (3 to 6 weeks) post infection. While there is some difference in the time to positivity of the various types of HIV antibody tests, the HIV antibody test by ELISA (b) would be no more likely to be positive this early than the latex aggregation test. The western blot for HIV antibodies (e) is used to confirm positive screening tests for antibodies. The CD4 T-cell count (a) is used to assess status of the immune system, determine the timing for treatment, suggest the likelihood of onset of various opportunistic infections, and monitor progress response of the immune system to treatment. The count is unlikely to be decreased at 2 weeks post infection although a drop does coincide with the peak of viremia. [/INST] question: A 27-year-old man presents to his primary care physician with complaints of a fever, headache, muscle aches, and swollen glands. The physician observes disseminated lymphadenopathy, pharyngitis, and a rash on the man's upper chest. The patient states that he had been to a party 2 weeks ago where he experimented with injecting drugs to get high. Needles were shared among the party-goers. A rapid latex test for human immunodeficiency virus (HIV) antibodies performed in the physician's office is negative. The doctor has a strong suspicion that this man has acute retroviral syndrome. Which of the following tests is most likely to support a diagnosis of HIV infection at this time? | options: A: CD4 lymphocyte count B: HIV antibody test by enzyme-linked immunosorbent assay (EIA) C: HIV p24 antigen D: Reverse transcriptase polymerase chain reaction (PCR) for HIV RNA | answer: D </s>