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I have a healthy patient without HIV risk factors who asks about HIV screening. How do I diagnose or exclude HIV infection?
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PATIENT 
Mr. A asks his new primary care physician whether he should get an HIV test. He states that he has “absolutely no risk factors for HIV.” He is a very healthy 21-year-old African American man who has been in a monogamous relationship with his current girlfriend for 2 years. The girlfriend was tested for HIV 6 months ago when a Board of Health nurse notified her that she might have been exposed to HIV, and retested 3 months ago. Both HIV tests were negative, effectively ruling out HIV infection.
Mr. A first became sexually active at age 15. Over the last 6 years, he has had only 4 female partners, although with a bit of overlap between the relationships (he had 2 simultaneous partners for about a year). He has never had sex with a male. He used condoms “pretty consistently.” He had Chlamydia trachomatis urethritis 3 years ago, but no other sexually transmitted infections (STIs). He has never used injection drugs although he smokes marijuana once or twice a week. He stopped drinking excessively when he met his current girlfriend. He does not recall an episode of mononucleosis-like illness with fever and lymph node enlargement. His past medical history, review of systems, and physical exam are otherwise unremarkable.
Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?
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Leading Hypothesis: Universal Screening for HIV Infection
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Textbook Presentation
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Chronic HIV infection may present in a myriad of ways. Many patients are entirely asymptomatic in spite of long-standing HIV infection and advanced immune deficiency as demonstrated by an absolute CD4 T lymphocyte (CD4TL) count below 200 cells/mcL (immunologic AIDS). Some patients may have symptoms that are often seen with HIV but are nonspecific, such as chronic diarrhea or nonspecific skin findings (seborrheic dermatitis, multiple molluscum contagiosum, poorly responsive psoriasis and prurigo nodularis). Other patients have conditions that are strongly associated with HIV infection but are also encountered in non–HIV-infected persons, such as tuberculosis (TB), idiopathic thrombocytopenic purpura, nephropathy, cardiomyopathy, herpes zoster, and non-Hodgkin lymphoma. Unfortunately, too many patients are discovered to have HIV only when they are admitted to the hospital with a life-threatening AIDS-defining condition, such as Pneumocystis jirovecii pneumonia (PCP), Cryptococcus meningitis, central nervous system (CNS) toxoplasmosis, or primary brain lymphoma.
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Prevalence and incidence of HIV in the United States
The Centers for Disease Control and Prevention (CDC) publishes yearly detailed data describing the HIV epidemic in the United States.
1,144,500 adolescents and adults lived with HIV (2010).
15.8% were not aware of their infection.
Over the past decade, the prevalence of HIV has increased because HIV-infected people live much longer.
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