Human immunodeficiency virus (HIV) is a major public health concern, with approximately 1 million persons in the United States infected. Of these persons, 24 to 27 percent do not know that they have HIV infection. Approximately 36 percent of new cases are transmitted by persons unaware that they are infected. HIV testing is typically done with enzyme immunoassay and follow-up immunofluorescent assay or Western blot. This test sequence has a sensitivity of more than 99 percent and specificity of more than 99.99 percent.

The American College of Physicians (ACP) guideline presents the evidence on screening for HIV in adults and adolescents older than 13 years. This guidance statement was developed from an evaluation of guidelines from the U.S. Preventive Services Task Force (USPSTF) and the Centers for Disease Control and Prevention (CDC).

Guidance Statements

Physicians should routinely screen patients for HIV, and encourage them to be tested. The goal of HIV screening is to identify persons who have undiagnosed HIV infection to provide treatment and prevent transmission. The ACP recommends instituting routine screening of all patients because early identification and treatment can lengthen the life of a person with HIV infection and possibly reduce transmission; because risk-based screening has not been shown to identify a large number of persons with HIV infection early in the disease; because routine screening in all persons unless they decline (opt-out screening) is widely used and highly successful in prenatal HIV screening; and because evidence shows that routine screening is cost-effective, even if the prevalence of HIV infection is low.

The ACP also recognizes the importance of screening pregnant women and high-risk persons, including men who have sex with men; persons who have unprotected sex with multiple partners; previous or current injection drug users; persons who exchange sex for money or drugs (or who have sex with persons who do); persons who have sex with persons who have HIV infection, are bisexual, or use injection drugs; persons who are being treated for sexually transmitted diseases; and persons who had a blood transfusion between 1978 and 1985. Screening is also important for persons who have been receiving care in high-risk health care settings, such as correctional facilities, homeless shelters, and tuberculosis clinics. The American College of Obstetricians and Gynecologists, the CDC, and the USPSTF all recommend that pregnant women be screened for HIV.

The CDC recommends HIV screening in persons 13 to 64 years of age. Although about 20 percent of persons with HIV infection are older than 50 years, few data exist on the benefit of screening in older persons. One analysis showed that screening persons up to 75 years of age met standard cost-effectiveness thresholds if the patients were having sex, if the screening was done in combination with counseling, and if the prevalence of HIV infection was higher than 0.1 percent in the population. Because the prevalence in most populations is not typically known, one approach would be to begin routine screening, and if a large number of persons T are tested and no cases of undiagnosed HIV infection are discovered, the need for screening should be reevaluated. Physicians should talk with their patients about risk factors for HIV, especially younger and older populations who may not be aware that certain behaviors put them at increased risk.

False-positive results are rare with enzyme immunoassay followed by Western blot (traditional testing), but the results are not available quickly. Rapid tests provide results within one hour of testing, but oral versions have increased false-positive rates. Positive results with rapid tests should be confirmed with traditional testing.

Physicians should determine the need for repeat screening on an individual basis. The need for repeat HIV screening depends on whether the patient has an ongoing risk of infection. Patients at higher risk should be retested more often than those at lower risk. The USPSTF recommendations do not discuss the frequency of screening, but the CDC recommends that physicians screen high-risk patients at least once a year. One good-quality analysis supported the cost-effectiveness of the CDC recommendation to screen high-risk persons once per year. However, apart from repeat screening in high-risk populations, the choice to rescreen should be based on clinical judgment.