Diagnosis of primary HIV-1 infection

Background: The optimal approach for diagnosing primary HIV-1 infection has not been defined. Objective: To determine the usefulness of symptoms and virologic tests for diagnosing primary HIV-1 infection. Design: Prospective cohort study. Setting: A teaching hospital in Los Angeles and a university research cente r in San Diego, California. Patients: 436 patients who had symptoms consistent with primary HIV infecti on. Measurements: Clinical information and levels of HIV antibody, HIV RNA, and p24 antigen. Results: Primary infection was diagnosed in 54 patients (12.4%). The sensit ivity and specificity of the p24 antigen assay were 88.7% (95% CI, 77.0% to 95.7%) and 100% (CI, 99.3% to 100%), respectively. For the HIV RNA assay, sensitivity was 100% and specificity was 97.4% (CI, 94.9% to 98,9%), Fever, myalgia, rash, night sweats, and arthralgia occurred more frequently in pa tients with primary infection (P < 0.05). Conclusions: No sign or symptom allows targeted screening for primary infec tion. Although assays for HIV RNA are more sensitive than those for p24 ant igen in diagnosing primary infection, they are more expensive and are more likely to yield false-positive results.