Prevalence of primary HIV infection in symptomatic ambulatory patients.

Purpose: Recognizing primary human immunodeficiency virus (HIV) infection is important for public health. The prevalence in outpatient settings is largely unknown but would be useful in developing testing guidelines. The objective of this study is to estimate the national prevalence of primary HIV infection in symptomatic ambulatory patients regardless of risk factors.

Methods: Patients 13 to 54 years old with each of 17 primary HIV infection symptoms, as well as other reported reasons for their visit consistent with primary HIV infection, were identified from the 2000 National Ambulatory Medical Care and National Hospital Ambulatory Medical Surveys to provide the denominator for the prevalence estimate. These survey data can be extrapolated to represent 90% of all US ambulatory care visits, including those to physician's offices, emergency departments, and hospital clinics. Patients with symptoms and diagnoses inconsistent with a viral illness were excluded. The estimate for the numerator was derived from Centers for Disease Control and Prevention estimates and the medical literature.

Results: Patients complaining of fever and other visit reasons consistent with primary HIV infection had a disease prevalence of 0.66% (0.57%-1.02%), those with rash had a prevalence of 0.50% (0.31%-0.82%), and those with pharyngitis had a prevalence of 0.16% (0.11%-0.22%). Patients with other symptoms represented numbers of visits insufficient for reliable estimates of their prevalence.

Conclusions: These estimates of the prevalence of primary HIV infection in ambulatory patients with fever, rash, and pharyngitis can aid with development of clinical testing guidelines and clinical decisions around testing for acute HIV infection.