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Specifics of the CDC recommendations are (MMWR 2006;55RR14):
- The test should be considered a routine component of health care for persons 13 to 64 years of age and should be obtained in common health care settings such as emergency rooms, primary care clinics, hospital admissions, birth control clinics, and STD clinics. (Persons > 65 years are not included for routine testing because the overall seroprevalence in that population is <0.1%, which is the threshold for cost-effectiveness (NEJM 2005;352:570).
- Consent to the test would be implied by consent to receiving care in these settings; patients can refuse to be tested as they may refuse any test or procedure.
- Patients should be made aware that they will be tested for HIV and be given the option to refuse the rest or request more information and this decision would not jeapordize their future care.
- Patients with positive tests should be referred for HIV care.
- High risk patients (defined above) should be tested at least annually.Others should not be retested unless there is a new risk such as a new sex partner.
- Test results should be communicated to the patient like any other test result. Patients with positive screening tests will require a confirmatory WB and referral to an HIV provider.
- It should be emphasized that the CDC recommendations are not against counseling about HIV prevention, stigma, etc; it is that these issues should be managed like other sensitive medical issues without mandating specifics (see AIDS 2007;21:1617).
Standard Test
The standard serologic test consists of a screening enzyme-linked immunoassay (EIA) or a rapid HIV test followed by a confirmatory Western blot (WB). EIA screening requires a “repeatedly reactive” test, which is the criterion for WB testing. WB detects antibodies to HIV-1 proteins, including core (p17, p24, p55), polymerase (p31, p51, p66), and envelope (gp41, gp120, gp160). WB testing should always be coupled with EIA screen-ing due to a 2% rate of false positives. Results of WB are interpreted as follows (Am J Med 2000;109:568):
- Negative: No bands.
- Positive: Reactivity to gp120/160 plus either gp41 or p24.
- Indeterminate: Presence of any band pattern that does not meet criteria for positive results.
ACCURACY: Standard serologic assays (EIA and WB or immunofluorescent assay) show sensitivity in patients with established disease (>3 months after transmission) of 99.5%(CI 98-99.9%) and a specificity of 99.994% (NEJM 2005;352:570; JAMA 1991;266:2861; Am J
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